Osage belly 1/4 sawn @ 1/4" thick, leave it parallel. Walnut core 1/4" thick, tapered from end of riser to 1/8" thick at tips. Hickory backing 1/8 th thick, you want perfectly straight grain hickory with very minimal run out and 1/4 sawn. The Osage belly should also be very straight grain with minimal run out. 1 1/4" wide at flares, maintain the 1 1/4" width out 6" past the flares then do a straight taper to 1/2" wide at tips. I would make the bow 62 to 64" long, with a 13" riser. But I don't know what hill bow specs should be. But wood grain choice is mandatory for these glue ups. You want very nice material.