diff --git a/src/toast/instrument_sim.py b/src/toast/instrument_sim.py
index fbffb246b..a2b1e59eb 100644
--- a/src/toast/instrument_sim.py
+++ b/src/toast/instrument_sim.py
@@ -568,10 +568,13 @@ def fake_hexagon_focalplane(
 
     """
     width_deg = width.to_value(u.degree)
+    # When laying out the hexagonal pixels, the angular "width" is the distance
+    # between the flat sides.
+    width_flats = np.cos(np.pi / 6) * width_deg
     pol_A = hex_pol_angles_qu(n_pix, offset=0.0)
     pol_B = hex_pol_angles_qu(n_pix, offset=90.0)
-    quat_A = hex_layout(n_pix, width_deg, "D", "A", pol_A)
-    quat_B = hex_layout(n_pix, width_deg, "D", "B", pol_B)
+    quat_A = hex_layout(n_pix, width_flats, "D", "A", pol_A)
+    quat_B = hex_layout(n_pix, width_flats, "D", "B", pol_B)
 
     temp_data = dict(quat_A)
     temp_data.update(quat_B)
@@ -624,7 +627,7 @@ def fake_hexagon_focalplane(
     return Focalplane(
         detector_data=det_table,
         sample_rate=sample_rate,
-        field_of_view=(width + 2.1 * fwhm),
+        field_of_view=1.1 * (width + 2 * fwhm),
     )
 
 
diff --git a/src/toast/scripts/toast_benchmark_ground b/src/toast/scripts/toast_benchmark_ground
index 39a08639e..e150cc0e5 100644
--- a/src/toast/scripts/toast_benchmark_ground
+++ b/src/toast/scripts/toast_benchmark_ground
@@ -185,7 +185,6 @@ def parse_arguments():
         2054  # Hex-packed 1027 pixels (18 rings) times two dets per pixel.
     )
     args.width = 10.0
-    args.fov = 1.1 * args.width * u.degree
     args.psd_net = 50.0e-6
     args.psd_fmin = 1.0e-5
 
@@ -460,7 +459,6 @@ def main():
 
     # Simulate atmosphere signal
     job_ops.sim_atmosphere.detector_pointing = job_ops.det_pointing_azel
-    job_ops.sim_atmosphere.field_of_view = args.fov
     job_ops.sim_atmosphere.apply(data)
     log.info_rank("Simulated and observed atmosphere in", comm=world_comm, timer=timer)
 
diff --git a/src/toast/scripts/toast_benchmark_ground_setup b/src/toast/scripts/toast_benchmark_ground_setup
index 562f22248..cf74de344 100644
--- a/src/toast/scripts/toast_benchmark_ground_setup
+++ b/src/toast/scripts/toast_benchmark_ground_setup
@@ -92,9 +92,8 @@ def parse_arguments():
     args.dry_run = None
 
     # Focal plane- we will use a dummy focalplane with just 2 detectors.
-    args.sample_rate = 1.0  # sample_rate is nb sample per second.
+    args.sample_rate = 100.0  # sample_rate is nb sample per second.
     args.width = 10.0
-    args.fov = 1.1 * args.width * u.degree
     args.psd_net = 50.0e-6
     args.psd_fmin = 1.0e-5
 
@@ -309,7 +308,7 @@ def main():
     if world_comm is not None:
         world_comm.barrier()
     job_ops.sim_atmosphere.detector_pointing = job_ops.det_pointing_azel
-    job_ops.sim_atmosphere.field_of_view = args.fov
+    job_ops.sim_atmosphere.field_of_view = telescope.focalplane.field_of_view
     job_ops.sim_atmosphere.cache_dir = cache_dir
     job_ops.sim_atmosphere.cache_only = True
     job_ops.sim_atmosphere.apply(data)