I had a similar problem with the Tred Avon. I used wedge shims successfully. I simply measured the amount that the beam needed to be raised, and the distance over which to bring it up. These translate to the thickness of the wedge and the length of the taper. I then cut two wedges, and glued them over the beam with a hold-down peice over the top of the whole asembly, like adding a lamination. It worked well. I was limited to a little over 1/8" thick by the 18" radius, it was too hard to bend thicker wedges. Some beams had two layers.

I dont think steaming epoxy will work, the glue will soften and give at temperatures above about 130F. Give it a try, the worst case is that you have to reglue a beam. There is a formula for the springback, check the archives.