Well, I am honestly not sure. I am relatively new to the whole gymnastics thing myself (started at 14 roughly 8 months ago) and I am trying to get skills needed to start competing Xcel :) my goal is to start competing this fall or next year.
Haha boy do I have one today. So I was doing a back hip circle (bet you are wondering how I fell on this one) and I casted too big into it...so about the time that I was completely under the bar, I flew off, and did a half- layout thingy do. I ended up facedown on the mat in a fit of giggles.
Hope I don't get my head bit off for this, but have you thought about using your mattress to learn your backbends? Me and my sisters did, and we picked it up fast.