Don, like I said, if you find the backing too thick while tillering or you just want the backing tapered a bit, you can do that after glue up. I have tillered from the back on a few hickory backed bows with no ill effects.
I have used hickory backings on osage, ipe, yew, hickory, mulberry, locust and probably other woods and never bothered to taper the hickory backing first. On bamboo it is different. If you don't cut the shape first then taper the backing it will be quite thick at the tips because of its crown. I don't think this is bad, except for appearance wise, because the boo is quite a bit lighter(physically) than most belly woods.