My using 120 film in a 616 camera is up on Photojunkie.org this week.

In case anyone is wondering it turns out that I didn't need to put any sort of frame inside to prevent light leaks. All I did was tape the outside seams of the camera as I do the toy cams and that worked just fine. I usually don't have that sort of bad seal with the box cameras so I wasn't expecting that to be the problem. But happily it was.