I work for a company that makes seat frames (I run a CNC Router). We also glue the foam to the frame before it goes off to the upholsterers. Theres lots of spare foam from the trimming etc. All different sizes and thicknesses. Its what I use to wrap the rx.
I've done this in lieu of using just velcro (rx sticks to side of fuse). I lost a nice Cessna Skylane because of a fractured xtal because it vibrated so much while velcro'd to the inside fuse wall. I've been using foam ever since.

Dave...