Bronica SQ-A cameras are great overall cameras. One weakness undermine the substantial goodness of their design: the flawed film backs. Besides the usual decay of the foams used as light seals (usual because found in several, if not all, cameras of the same age), a poorly designed plastic part (the grey rectangular plate, kept in place with 10 tiny screws) that cracks with use and has the same effects as a decayed light seal makes the whole system vulnerable.
The best light seals replacement are nowadays sold by Jon Goodman (email: firstname.lastname@example.org), Texas, USA. However, even him cannot be useful if the plastic part cracks.
In my opinion the most reliable way of using SQ cameras today is giving up to the interchangeability of the film backs and using some black electric tape or gaffer tape (a 6mm-wide strip) to cover the thin aperture for the dark slide. In this way the camera is “permanently” glued to the film back, tat can be opened to change film but not removed (via dark slide) to change roll before its end. Doing so, and provided that the other light seals are tight, one can ignore the inefficiency of the dark slide light seal and use the camera.
This is the theory: I had to test the film back and I found the Pink Lane in Newcastle was giving me a couple of photo opportunities. It seems that the darker and the dodgier the area is, the more attractive the photographic opportunities become. I found out that in “testing mode” I took, perhaps obviously, several shots that I would otherwise have not, and yet they turned out to be good – as well as the gaffer tape solution.