I like to rip the Osage board so I can get two bows out of it. I wind up with two 1/4" belly lams. I make the hickory backer 3/16" tapering to 1/8" at the tips. A 3/16" power lam (I like red elm, but maple, walnut, etc. is fine) 36" long gives me ample thickness for a 45 to 50# bow. You can make the power lam much shorter, but it's easier for me to get good glue lines with a longer one. Last 45# bow I made was 1 1/2" wide at the fades and just a hair over 1/2" thick at the end of the fades. Nice thing about hickory is that you can always take wood off the backer in a pinch if it's good, straight grain.