I have a Giles 300 and I had that same problem I would start a loop and when I applied more elevator to make it a tighter loop it would always snap out to the right violently too. I did some experimenting flying inverted and pushing forward on the stick and pow it almost flipped upright and over with no snap. I concluded that i had possibly a throw that was off or maybe an incidence issue. Because I had duel elevator servos I set the travel on the right one less than the left until I could haul back on the stick and it wouldnt snap. That worked for me now its an awesome plane to fly. That may not be the text book way to correct this but like I said no more snapping.