You don't always need tape at the seam. What you do need is a way to precisely align the two halves when joining them. Your existing molds can probably handle that task.

There are glider builders, for example, building tremendously strong wings in two halves, using only epoxy/Cabosil or epoxy/microballoons to join the two parts. Some people have also suggested epoxy/milled glass, or epoxy/chopped cotton fibers. Until recently, I've always assumed that the fibers (or tape) were required, but now we know they are not. There's apparently not enough stress concentrated on these seams to warrant the overkill in materials we've been using.