I retried my 90mm with and without the condensors in place. I believe that it requires a conical lensboard to obtain the proper spacing because I ran out of bellows extension just as image began to focus. Also, largest image possible is 5x7(barely) with the longer focal length lens, as it acts as a telephoto with 35mm format. After rereading my owners manual, I got it to work properly. I even got my 105mm, 135mm, and 150mm lenses to focus on the C-700. Keep in mind, that you can use the shorter focal length lenses with larger format, acting as wide angle(if you dont try too big a neg. with too small a lens)and get a greater enlargment size with less head elevation. Its possible to get 20x24 using 50mm with 6x6 neg. without turning the head. well, have fun with your machine, and experiment. Thats the fun of having a darkroom.
Rick