Two months, and nobody had replied?
Well, I haven't had any need yet to make my own plate holders. I'm getting closer to making my own plate camera to fit some of the holders I have, though - among them several stereo plate holders that might make a nice little panorama camera. With a decent lens for 4x8", which shouldn't be too difficult. I think a 90/8 Super Angulon could do it, or something else I'm sure to have lying about already. Weitwinkel-Aristostigmat or something.