I now have a Horseman 45 HD. I have mounted a 150 G- Claron and a 203 Ektar. Both lenses fit inside the camera when folded. I am looking for a faster 150mm that will also fit. I would like it to mount in a Copal #o on a flat board. Big coverage is not needed. Would a f/5.6 Caltar/Rodenstock work? Or how about a newer 150 Xenar?