I recently stumbled upon a YouTuber called "pigmie" who didn't get over the fear of doing a double backflip as he could land on his head and get a serious injury. So he build his own protection (the "moonsuit"):
https://www.youtube.com/watch?v=4jnfqBUw6gg <--- minute 1:00
This moonsuit is build out of many pieces of a (rather thin) gymnast-mattress. And he got over the fear!
But this suit is not really secure ... I mean, it's hard to get a serious head-neck-back injury with it, but its still not as convenient as I wish my protection to be!
This is how he build it: https://www.youtube.com/watch?v=DkmngpiISf0&t=627s
But there must be an easier protection... maybe a neck-protection with a motocross-helmed or a ruff? I don't know if thats a good idea...?
What's important is that I should still be able to do front and backflips and that my back is safe from overbending too!