Thanks for spending the time to analyse. The outer elevons are used as intended but the small inner elevons I've been experimenting with as flaps and differential spoilers. The inner servos have just enough cable to reach Main Output 1 and 8 - saves having extensions just for a cm.
The CoG is the same as before I switched the Pixhawks so I don't think that was a factor. The FX-79 does not normally need 100% throttle but there was a little cross wind so I just wanted it away from the ground asap. I normally auto-take-off to run missions and set the max FBW throttle to 75%. This was going to be a simple autotune maiden.
The P2 was removed from an A tail plane and put into the FX-79. I thought that the parameters were reset because I loaded the latest copter firmware and then loaded arduplane again but it looks like I did not do that properly if the old A tail parameters are still there. I probably tried to maiden with all the PIDs for the A tail. :-/
The FX-79 does not have a tail..... yet! We have plans to add an A tail so it can be dropped from a balloon and have better control at high altitudes. I've not found a reliable way to mount that tail yet without filling the wings with carbon but then I can't detach the wings so it will not fit in the car. This photo is potentially how it would look with the tail fitted. Ignore the grey wings
It's now rebuilt and ready for another maiden on Wednesday