The unit works well in an electric or a jet.
I have been ground testing it in a 15cc powered gas powered biplane. The vibration causes the AHI to wander off scale. I soft mounted the engine and mounted the unit on double stick foam tape but it still drifted off.
I think there is a way to make it work but it will take some study. The trick is to isolate the vibration while still getting the AC movement to it.
I have used it on an electric AC and the 2d mode makes flying like driving a car. You have to hold the aileron over to make it turn. It wont let you roll more than 60 degrees.
Flying in 3d mode it just corrects for disturbances like wind.
If you get one remember the servo battery will go done fast as the servos are moving all the time.