Hey man,
Doing backflips in the BC are actally, in my opinion, way easier than back flips in the park. The key for the BC is setting the flip. Usually the take off is flatter in the BC as you are not taking off a jump, so you really need to be careful in setting it with your HIPS, not your head, cause from a flat takeoff, that can get hairy. Plus, same as the park, have the timing in the air down for the drop before you attempt the flip. Also, if it is soft snow, you want to over rotate a tiny bit, not much, but enough to not come down flat and cartwheel . You need your ski tips to stay above the snow- You need to be aware of the angle of the landing for this. For the take off, be sure it is stable, and there are no rocks right underneath your takeoff, cause that will hurt! For it to be stable, get out on it and stomp it out, and be sure it doesn't fall like a cornice or something.
I love throwing huge floaty backs in the BC. 40-50 footers really let you just lay back and feel like you are upside down forever! That is pretty much the biggest rush in skiing, actually not pretty much, absolutely is the biggest rush!