For an r/d design, straight grained hickory makes an excellent backing material. Strong, resilient, and inexpensive. If you've ever split a hickory log, you'll experience the interlocking fibers...they're a pain in the butt! While hickory is tough stuff, it can be thinned or trapped so as not to overpower any belly wood you use, minimizing set (caused by overcompression). Personally, I've not had good experience with maple.
For a r/d bow bamboo ranks at the top of the heap for me, though the quality of bamboos can vary widely.