Think it's what Slimbob said: don't look to the backing, look to the bow. Some types of wood pretty much ought to always be backed because such and such a wood is weak in tension but good in compression. Ipe is an example of this as are cherry and juniper. Not to say they can't be made into self bows, but a backing on them is much safer and improves their lifespan. Most other "bow woods" don't really need a backing IF you select the appropriate piece of wood. Like Slimbob said: no runoff, knots etc... Backings are great when the piece of wood you are using isn't the best. In that case, bamboo, hickory, maple and ash are common hardwood backings. Sinew, rawhide ,linen, cotton, flax (? if I remember right) and silk are common "soft" backings. Sinew is sort of a different topic entirely. Skins are for decoration in most cases and aren't going to do much to keep anything from failing in tension. Although some archers hate hearing this, two big rawhide dog-chews will work for a "rawhide backing" when spliced at the handle. This is not the high quality rawhide most archers want to use and it is highly processed, but in most situations, it is plenty strong. Rawhide goes a long way and isn't as difficult to apply as a wood or sinew backing. It also won't overpower the belly of the bow causing chrysals. Good choice I think.
