Hey Ifrit,
How thick is the billet? I know you said you roughed it out 1.5" wide the whole way down but if you're billet is say 1.5" wide x 35" long and 1" to 1.5" deep you could split it down the length and probably have enough to do a handle splice. I've heard of guys splitting a thick stave this way to get more bows out of it. Actually I think Pappy had a pretty nice snakey osage on here before from something he did with that, but I could be wrong about that. See how thick the bow is and how many rings per inch you got, see if you have a way to split it between two rings where you end up with two billets at least 1/2" thick. That should be thick enough to get you in the 40#-45# range at 28". Most of my bows my starting dimensions are to taper from 5/8" at the fades and I start moving wood from there. Just an idea though.
~Barry