I can do back somersaults on a trampoline, and I spent a whole weekend doing them on a trampoline and bouncy castle before i tried them on bocks, so that i was confident with landing them.
The sliding mats and support is similar to the way it is taught on the trampoline, so its there to give me more confidence that I am safe if it goes wrong. Nero wasnt actually doing anything, so him letting go was to prove to me that I was doing it all by myself!
I am still unbroken for now, although I had another attempt at a backflip on grass this weekend - thought it was a good idea - however i now think several copies of my backflip landing on my knees in a field will appear on youtube as i had a lot of network watching and filming!