Hi I have the same plain and mine fly's like a dream. Make sure youd SG is not to far back and the elevator should not move more than 20 mm up or down on maximum input on the stick. I do Sportsman Precision Aerobaticks with mine and I must tell you there is already about 3 people that also whant to buy the same plain. Maibe you can try to move your SG more to the front, mine is about a 90 mm back of the leading ege of the wing closest to the fuse.

Try that and see what happens.

Good luck

Arrie