In theory, no, it's not enough for a glow or gas engine.

However, RX's are better than they used to be. I've seen many mounted with less padding than you describe and not have any problems at all. I doubt you'd have a problem.

Just do the best you can, and remember that if it does fail, it will cost you a lot in terms of the destroyed model. So extra effort to get a better installation is well spent.

I've done things where I had padding top and bottom, but nothing touching on a side for example.