You need to do it before if its going to be more than what you can induce during the glue up...and you also need to thickness taper it before glue up(unless you want a straight glue up)...lots to say and for you to learn in how to properly taper your lams pre glue up...if ya wanna induce a nice even shape and put the bends where there supposed to go they need to be tapered down and def reduced more than an inch so it'll bend easier.....the more work done pre glue up the easier it is...80%+ of the work is done pre glue up....if your osage board is an inch+ thick then you prob have two bows in it,or at least one belly piece and one core piece for maybe a tri lam later down the road once you make some more lam bows and get the jist of it down well....in simple terms make the handle section a half inch thick parallel,and then from the fades taper it to 3/8" thick at the tips for normal bunting weight flat bows...
And no need to put extra work kerfing for your curves with osage....it heat bends super easy and none other woods can compare IMO....especially at those thicknesses with dry heat...but if going for sharp shorter statics then you'll need to steam them in
