Kip, Never had the urge to get into the ELB thing, as far as backers go I know that Ken uses hickory, and I have used maple, ash, birch, white oak, and red and grey elm.
If you want a combination that is almost bullet-proof I would strongly recommend the hickory or elm. The rest are almost as good....and none are "bad" choices.
If you decide on a self bow remember that walnut will need to be slightly thicker than say, hickory, maple, ash or the like. For example, if you have made a hickory bow of a certain weight and it was 3/8 to 1/2 inch thick I would make the walnut 3/4" and work it down a little to maybe 9/16 or so to make the same weight.
Would love to send you some pics, do you want them on here or sent to your regular email address?
Rich