Sorry I’m, a bit late to the party on this thread as I only found this forum today by accident when looking for something else.
Did you ever get to the bottom of this issue at all?
one possible cause for this can be the centre wing panel on the upper surface of the wing if the Velcro fasteners on its edges aren’t sealing so well any longer. The propwash at full power will suck some air out of the wings flattening the wing profile slightly and giving and aggressive pitch down with with power which is restored again when you close the throttle.
All the other explanations given previously are definite possibilities, but I have seen this particular issue on a Thruster before caused by the centre panel not sealing well.
regards,
Simon
