As EASmithV has suggested, a sheet of ground glass in the film pack adapter is an easy solution. It is automatically set for the proper focal plane (same as the film pack would be) and the adapter fits the camera perfectly - no jury-rigging. The only drawback I have with the one I made is that the glass I used is somewhat heavier than standard and the back has no hood to darken the area around the image for work without a dark-cloth.