For some dumb reason that escapes me at the momment, I didn't make my outer stems at the same time as the inner stems. After the canoe was all planked I made a cardboard template that fit over the inner stems. I traced this curve to a piece of plywood. Then I attacked 1"x2" blocks along the inside of this curve. With the blocks of wood mimicing the shape of the inner stems, I bent the outer stems around my form. The fit wasn't perfect, but when I clamped the outer to the inner with about 6 screws it was close enough to glue it up.