I haven't used persimmon yet, I just cut some a couple weeks ago though. All the rest are very tension strong and require no backing. They do perform well with a belly heat treatment. Your elm looks pretty twisted, I'd pass on that particular one and see if you can find a smaller straight one to tackle. Also with elm, it has a nasty habit of twisting and warping when drying. Once you peel the bark, split em and seal the ends, you'll want to lash em to something to keep em straight. Even lashing them back together the way were before you split them will help. After they've dried for a couple months, they are pretty well stabilized and you can unlash them and let the air circulate around them more. Josh