Oh yes, there's plenty of leeway on the front sleds. The 18cm Eurynar I've been using isn't really all that (hazy elements), but it's slightly closer to the focus scale with the back on, and I've just scored an old Freidrich Coronar 13.5cm and a 6" no-name which will probably suit. The front of the camera has a 44mm(approx) threaded lens mount, so I have a great deal of flexibility there.The focal plane moved back a bit, right? Can you still focus at infinity?
The focus scale on the camera when I got it, is a home-made one, though what lens matched it I don't know.