1 1/4" to 1 1/2" is plenty wide for a 65", 50#-55#@27" osage bow. You could go with a pyramid style, straight taper from the fades to the tips or go out 6" to 8" before tapering to the tips. Try to work it out so you eliminate the pins and knots and if you can't, leave as much wood around them to make them more safe.