Troy, I know this is a bit off topic, but there are a lot of guys making wooden bows... backed bows, trilams, and such, and suppliers for good, full length, hickory, maple, white oak, etc backings are few and far between. Perhaps you don't want to bother, you're probably busy enough with glassbow lams, but I'm pretty confident folks would jump on them.
Quartersawn pieces 1/8 x 1 3/4 to 2" x 72" would work.
Sorry for the sidetrack.