So, I'm using a trampoline, and can do a front tuck, front half, and probably a front full (whatever I'm doing isn't hard, and feels like a front full, but there's no one around to watch and verify...I need to find a video camera).

Going backwards, I can very easily do a back tuck (even on ground, no problem), and I can do them way high up, and way laid out.  I might even be able to do a double...I've tried to twist for a back half, look over the shoulder, do something with my arms, but nothing happens!!  How do you start twisting?  What should my arms be doing?

Thanks, that makes some sense, and is something I haven't yet tried.  I've been mostly throwing my right arm up and to the left, punching towards my left shoulder (I spin counter-clockwise when viewed from above too), a lot like anis' cork tutorial...
I'll wait till someone else is home to call the morgue before I give it another shot :-)