I'm working on a few myself. Just strip the bark and you're good, no need to back. I've read good things about elm. I made one a while back from a sapling, ~50#, narrow D style.
The only thing I'd say to be wary of is elm likes to form spiral grain so make double sure you're following it when laying out the bow. Even following it carefully, I've had a few strokes with the drawknife pull up grain that wanted to travel into my outline. Thankfully I outlined a little oversize.