Wow, this thread is exactly what I've been looking for! I've been trying to find a way to compress my 36DDs in order to crossplay for the first time, but the ace bandages really restricted my breathing. The sport tape method sounds like the best route, even as an aid over a simple ace bandage --since it stated that it might not work with anything over a B.
I'm trying to get the flat chest look with the ability to breathe. Anyone who's been to the LA convention center knows there's a LOT of walking involved, and I don't want to pass out from the train station to the front door. I'll try this and see how it works out. Thanks for the helpful tips.