Mark, heat treating works well with most whitewoods. I've never worked maple so it's only a guess it works for maple. I personally would heat treat maple.
On the lam bows I've built I never used tapers. I cut the lams parallel, about 1/8" or so and once glued up I tillered just like a stave bow with the taper in the belly lam. You do have to be sure all the glue surfaces mate will. Also if you are going to heat treat the belly, do it before glue up. Heat deteriorates most glues.
I don't do many lam bows so take what I say with a grain of salt.