diff --git a/Makefile b/Makefile
index baff3fae1a7..827e74632f0 100644
--- a/Makefile
+++ b/Makefile
@@ -238,6 +238,10 @@ ifneq ($(SKIPCHECKS),yes)
 ifneq ($(filter-out $(SRC),$(SPEED_OPTIMISED_SRC)),)
 $(error Speed optimised sources not valid: $(strip $(filter-out $(SRC),$(SPEED_OPTIMISED_SRC))))
 endif
+
+ifneq ($(filter-out $(SRC),$(SIZE_OPTIMISED_SRC)),)
+$(error Size optimised sources not valid: $(strip $(filter-out $(SRC),$(SIZE_OPTIMISED_SRC))))
+endif
 endif
 
 ###############################################################################
diff --git a/mk/source.mk b/mk/source.mk
index bcce271f261..317d4c43552 100644
--- a/mk/source.mk
+++ b/mk/source.mk
@@ -391,7 +391,24 @@ SIZE_OPTIMISED_SRC += \
             drivers/accgyro/accgyro_spi_mpu9250.c \
             drivers/accgyro/accgyro_spi_icm20689.c \
             drivers/accgyro/accgyro_spi_icm426xx.c \
-            drivers/accgyro/accgyro_spi_lsm6dso_init.c
+            drivers/accgyro/accgyro_spi_lsm6dso_init.c \
+            drivers/barometer/barometer_bmp085.c \
+            drivers/barometer/barometer_bmp280.c \
+            drivers/barometer/barometer_ms5611.c \
+            drivers/barometer/barometer_lps.c \
+            drivers/barometer/barometer_qmp6988.c \
+            drivers/barometer/barometer_2smpb_02b.c \
+            drivers/compass/compass_ak8963.c \
+            drivers/compass/compass_ak8975.c \
+            drivers/compass/compass_hmc5883l.c \
+            drivers/compass/compass_qmc5883l.c \
+            drivers/compass/compass_lis2mdl.c \
+            drivers/compass/compass_lis3mdl.c \
+            drivers/compass/compass_ist8310.c \
+            drivers/display_ug2864hsweg01.c \
+            drivers/vtx_rtc6705_soft_spi.c \
+            drivers/vtx_rtc6705.c
+
 
 SPEED_OPTIMISED_SRC += \
             drivers/bus_spi.c \
@@ -467,41 +484,14 @@ SPEED_OPTIMISED_SRC += \
             $(CMSIS_SRC) \
             $(DEVICE_STDPERIPH_SRC) \
 
-SIZE_OPTIMISED_SRC := $(SIZE_OPTIMISED_SRC) \
-            $(shell find $(SRC_DIR) -name '*_init.c') \
-            bus_bst_stm32f30x.c \
+SIZE_OPTIMISED_SRC += \
+            sensors/gyro_init.c \
+            sensors/acceleration_init.c \
+            flight/pid_init.c \
+            flight/mixer_init.c \
             cli/cli.c \
             cli/settings.c \
-            drivers/accgyro/accgyro_fake.c \
-            drivers/barometer/barometer_bmp085.c \
-            drivers/barometer/barometer_bmp280.c \
-            drivers/barometer/barometer_fake.c \
-            drivers/barometer/barometer_ms5611.c \
-            drivers/barometer/barometer_lps.c \
-            drivers/barometer/barometer_qmp6988.c \
-            drivers/barometer/barometer_2smpb_02b.c \
-            drivers/bus_i2c_config.c \
-            drivers/bus_i2c_timing.c \
-            drivers/bus_spi_config.c \
-            drivers/bus_spi_pinconfig.c \
-            drivers/compass/compass_ak8963.c \
-            drivers/compass/compass_ak8975.c \
-            drivers/compass/compass_fake.c \
-            drivers/compass/compass_hmc5883l.c \
-            drivers/compass/compass_qmc5883l.c \
-            drivers/compass/compass_lis2mdl.c \
-            drivers/compass/compass_lis3mdl.c \
-            drivers/compass/compass_ist8310.c \
-            drivers/display_ug2864hsweg01.c \
-            drivers/inverter.c \
             drivers/light_ws2811strip.c \
-            drivers/serial_escserial.c \
-            drivers/serial_pinconfig.c \
-            drivers/serial_tcp.c \
-            drivers/serial_uart_pinconfig.c \
-            drivers/serial_usb_vcp.c \
-            drivers/vtx_rtc6705_soft_spi.c \
-            drivers/vtx_rtc6705.c \
             drivers/vtx_common.c \
             fc/init.c \
             fc/board_info.c \
@@ -509,7 +499,6 @@ SIZE_OPTIMISED_SRC := $(SIZE_OPTIMISED_SRC) \
             config/feature.c \
             config/config_streamer.c \
             config/simplified_tuning.c \
-            i2c_bst.c \
             io/dashboard.c \
             io/serial.c \
             io/serial_4way.c \
@@ -551,9 +540,6 @@ SIZE_OPTIMISED_SRC := $(SIZE_OPTIMISED_SRC) \
             io/vtx_msp.c \
             cms/cms_menu_vtx_msp.c
 
-SIZE_OPTIMISED_SRC := $(SIZE_OPTIMISED_SRC) \
-            drivers/bus_i2c_hal_init.c
-
 # check if target.mk supplied
 SRC := $(STARTUP_SRC) $(MCU_COMMON_SRC) $(TARGET_SRC) $(VARIANT_SRC)
 
diff --git a/src/platform/APM32/mk/APM32F4.mk b/src/platform/APM32/mk/APM32F4.mk
index 1c7d8c42a68..6172080a02a 100644
--- a/src/platform/APM32/mk/APM32F4.mk
+++ b/src/platform/APM32/mk/APM32F4.mk
@@ -203,5 +203,15 @@ MSC_SRC = \
 SPEED_OPTIMISED_SRC += \
         common/stm32/system.c
 
+SIZE_OPTIMISED_SRC += \
+        APM32/usb/vcp/serial_usb_vcp.c \
+        drivers/inverter.c \
+        drivers/bus_i2c_config.c \
+        drivers/bus_spi_config.c \
+        drivers/bus_spi_pinconfig.c \
+        drivers/serial_escserial.c \
+        drivers/serial_pinconfig.c \
+        drivers/serial_uart_pinconfig.c
+
 DSP_LIB := $(LIB_MAIN_DIR)/CMSIS/DSP
 DEVICE_FLAGS += -DARM_MATH_MATRIX_CHECK -DARM_MATH_ROUNDING -DUNALIGNED_SUPPORT_DISABLE -DARM_MATH_CM4 -DUSE_FULL_DDL_DRIVER
diff --git a/src/platform/AT32/mk/AT32F4.mk b/src/platform/AT32/mk/AT32F4.mk
index dda6847b9c2..66c04b4af36 100644
--- a/src/platform/AT32/mk/AT32F4.mk
+++ b/src/platform/AT32/mk/AT32F4.mk
@@ -128,3 +128,13 @@ MCU_COMMON_SRC = \
 
 SPEED_OPTIMISED_SRC += \
             common/stm32/system.c
+
+SIZE_OPTIMISED_SRC += \
+            drivers/bus_i2c_timing.c \
+            drivers/inverter.c \
+            drivers/bus_i2c_config.c \
+            drivers/bus_spi_config.c \
+            drivers/bus_spi_pinconfig.c \
+            drivers/serial_escserial.c \
+            drivers/serial_pinconfig.c \
+            drivers/serial_uart_pinconfig.c
diff --git a/src/platform/SIMULATOR/target/SITL/target.mk b/src/platform/SIMULATOR/target/SITL/target.mk
index 97a4d2bd2d3..c314728e480 100644
--- a/src/platform/SIMULATOR/target/SITL/target.mk
+++ b/src/platform/SIMULATOR/target/SITL/target.mk
@@ -7,3 +7,6 @@ TARGET_SRC = \
             drivers/barometer/barometer_virtual.c \
             drivers/compass/compass_virtual.c \
             drivers/serial_tcp.c
+
+SIZE_OPTIMISED_SRC += \
+            drivers/serial_tcp.c
diff --git a/src/platform/STM32/mk/STM32F4.mk b/src/platform/STM32/mk/STM32F4.mk
index e9a37cb186d..712940f5615 100644
--- a/src/platform/STM32/mk/STM32F4.mk
+++ b/src/platform/STM32/mk/STM32F4.mk
@@ -212,6 +212,15 @@ SPEED_OPTIMISED_SRC += \
             common/stm32/system.c \
             STM32/exti.c
 
+SIZE_OPTIMISED_SRC += \
+            STM32/serial_usb_vcp.c \
+            drivers/inverter.c \
+            drivers/bus_i2c_config.c \
+            drivers/bus_spi_config.c \
+            drivers/bus_spi_pinconfig.c \
+            drivers/serial_escserial.c \
+            drivers/serial_pinconfig.c
+
 ifeq ($(PERIPH_DRIVER), HAL)
 VCP_SRC = \
             STM32/vcp_hal/usbd_desc.c \
diff --git a/src/platform/STM32/mk/STM32F7.mk b/src/platform/STM32/mk/STM32F7.mk
index 9c294818157..2cf48120cc9 100644
--- a/src/platform/STM32/mk/STM32F7.mk
+++ b/src/platform/STM32/mk/STM32F7.mk
@@ -198,5 +198,16 @@ SPEED_OPTIMISED_SRC += \
             STM32/pwm_output_dshot_hal.c \
             STM32/exti.c
 
+SIZE_OPTIMISED_SRC += \
+            drivers/bus_i2c_timing.c \
+            STM32/bus_i2c_hal_init.c \
+            STM32/serial_usb_vcp.c \
+            drivers/bus_i2c_config.c \
+            drivers/bus_spi_config.c \
+            drivers/bus_spi_pinconfig.c \
+            drivers/serial_escserial.c \
+            drivers/serial_pinconfig.c \
+            drivers/serial_uart_pinconfig.c
+
 DSP_LIB := $(LIB_MAIN_DIR)/CMSIS/DSP
 DEVICE_FLAGS += -DARM_MATH_MATRIX_CHECK -DARM_MATH_ROUNDING -D__FPU_PRESENT=1 -DUNALIGNED_SUPPORT_DISABLE -DARM_MATH_CM7
diff --git a/src/platform/STM32/mk/STM32G4.mk b/src/platform/STM32/mk/STM32G4.mk
index 4131430398e..2c10613da38 100644
--- a/src/platform/STM32/mk/STM32G4.mk
+++ b/src/platform/STM32/mk/STM32G4.mk
@@ -171,5 +171,16 @@ SPEED_OPTIMISED_SRC += \
             common/stm32/system.c \
             STM32/exti.c
 
+SIZE_OPTIMISED_SRC += \
+            drivers/bus_i2c_timing.c \
+            STM32/bus_i2c_hal_init.c \
+            STM32/serial_usb_vcp.c \
+            drivers/bus_i2c_config.c \
+            drivers/bus_spi_config.c \
+            drivers/bus_spi_pinconfig.c \
+            drivers/serial_escserial.c \
+            drivers/serial_pinconfig.c \
+            drivers/serial_uart_pinconfig.c
+
 DSP_LIB := $(LIB_MAIN_DIR)/CMSIS/DSP
 DEVICE_FLAGS += -DARM_MATH_MATRIX_CHECK -DARM_MATH_ROUNDING -D__FPU_PRESENT=1 -DUNALIGNED_SUPPORT_DISABLE -DARM_MATH_CM4
diff --git a/src/platform/STM32/mk/STM32H5.mk b/src/platform/STM32/mk/STM32H5.mk
index b6c1682c7bb..21c0bd5a95f 100644
--- a/src/platform/STM32/mk/STM32H5.mk
+++ b/src/platform/STM32/mk/STM32H5.mk
@@ -205,5 +205,16 @@ SPEED_OPTIMISED_SRC += \
             common/stm32/system.c \
             STM32/exti.c
 
+SIZE_OPTIMISED_SRC += \
+            drivers/bus_i2c_timing.c \
+            STM32/bus_i2c_hal_init.c \
+            STM32/serial_usb_vcp.c \
+            drivers/bus_i2c_config.c \
+            drivers/bus_spi_config.c \
+            drivers/bus_spi_pinconfig.c \
+            drivers/serial_escserial.c \
+            drivers/serial_pinconfig.c \
+            drivers/serial_uart_pinconfig.c
+
 DSP_LIB := $(LIB_MAIN_DIR)/CMSIS/DSP
 DEVICE_FLAGS += -DARM_MATH_MATRIX_CHECK -DARM_MATH_ROUNDING -DUNALIGNED_SUPPORT_DISABLE -DARM_MATH_CM7
diff --git a/src/platform/STM32/mk/STM32H7.mk b/src/platform/STM32/mk/STM32H7.mk
index 5651cbd122b..2129a1e11a1 100644
--- a/src/platform/STM32/mk/STM32H7.mk
+++ b/src/platform/STM32/mk/STM32H7.mk
@@ -320,5 +320,16 @@ SPEED_OPTIMISED_SRC += \
             common/stm32/system.c \
             STM32/exti.c
 
+SIZE_OPTIMISED_SRC += \
+            drivers/bus_i2c_timing.c \
+            STM32/bus_i2c_hal_init.c \
+            STM32/serial_usb_vcp.c \
+            drivers/bus_i2c_config.c \
+            drivers/bus_spi_config.c \
+            drivers/bus_spi_pinconfig.c \
+            drivers/serial_escserial.c \
+            drivers/serial_pinconfig.c \
+            drivers/serial_uart_pinconfig.c
+
 DSP_LIB := $(LIB_MAIN_DIR)/CMSIS/DSP
 DEVICE_FLAGS += -DARM_MATH_MATRIX_CHECK -DARM_MATH_ROUNDING -D__FPU_PRESENT=1 -DUNALIGNED_SUPPORT_DISABLE -DARM_MATH_CM7