"I would not compromise the location of the gyro and accelerometer at all.  Best place is to mount it in the center of all three axis as calculated by CG or in the case of ballistic flight, the center of drag or use a calculator to find the average…"

"My system needs a manual flight mode for safety.  I don't have to hold the transmitter, but I do need some way to change flight modes in the air with a long range proven link.   I use my radio to switch to RTL flight mode when the telemetry gets out…"

"Of course, you need to do this work with the pixhawk and the GPS both mounted on the same frame and not loose.
I use the rotation selections in compass setup because the uBlox is sometimes upside down itself.  If this is a no name GPS or not, just…"

"What control board specifically is it? MultiWii or Arduino based?"

"Are you saying that EKF would have held the frame level when the gyro bias drifted?"

"Thank you for the info.  I appreciate your help.  I will study those variables."