not exactly what your looking for but...
used one briefly for photographing antique maps. worked fine on film, but when we put a digital back on (scanning back, covered the full 6x6 frame), there was too much color shift and fall off on the edges of the frame, so we ended up switching systems.
as far as the ground glass goes...we used it to set up the camera once, and marked off setting on the rail of the copy stand for focus points/map size, etc. It was for a collection of tens-of-thousands of maps, so we needed the fastest way of setting up and shooting.
ended up switching to a 4ft wide scanner for the project