ok, let me see if i can settle this dispute. i just got back (like 3 days ago) from a PSI camp at lake placid. every day before water ramping we would hit up the trampolines (flybeds) for an hour or two to warm up. all the kids there were cva kids mind you, so they train on flybeds every day in the school year. but they were doing cork 7, cork 9, and one of them tried a 10 mute, he couldnt do it without corking (and could right cork 9 and 7, with grabs). so the truth is, cork IS possible on a trampoline no matter what ANYONE differntly, and once you figure out how to do it, its easier than spinning flat. this might be just for flybeds, im not sure about the black circle ones, but i am 100% sure they are possible, and not hard!