Good point. While the GG on the Pentacon is way too small for that purpose, the one on my busted Flexora will definately do the job.
Either way, I have just shot a test roll on each camera, which if nothing else will tell me how the camera performs as I'll probably use it (f/8 and smaller). The slow shutter speeds pretty much dictate small apertures in sunny conditions... I think I only got as big as f/5.6 (shade), but mostly it was f/16.
Anyway, I'll try to develop these tomorrow, and we'll see how they turned out.
Hopefully better than a Holga, definately better than no 6x6 at all.