On the 351 gyro, can I use flaperons while in heading hold mode?
No. Flaperons may be activated and will operate normally in normal mode. This is the reason for the twin servo output capability. However, in heading hold mode the gyro will attempt to obey the input to the aileron channel and will go hard roll to the aileron channel on flaperon input. Please be aware though that you CAN use flaperons in “Normal” mode with no problems.