Don't forget there is more to 3d then CG you will need to experiment with throws, expo, and engine thrust lines to really get it tuned in
But I would start with the CG like YNOT said I would work it back slowly and fly it more the once at each setting if it gets too pitch sensitive or snaps out you have crossed the sweet spot
I'm playing a Magic 3d right now and found that adding some spoilers has help keep her from falling to the belly in a hover
so don't be afraid to play with all the settings but do them one at a time and 3 mistakes high till you get it where you want it
good flying