A while back I posted about a really nice "Universal" bellows I bought for my Sinar off of eBay. Well, it's a leaker. When it came I did the old flashlight in the darkroom test and no problems. Last weekend I shot some Fuji instant film, then some Polaroid type 52...so two different backs, and the film comes out fogged. Switched to the Sinar bellows and no problem with either film.
Back in the darkroom with the flashlight and I can't find a leak anywhere. I've emailed the company so we'll see what they do about it.
Sorry if I steered anybody wrong. It seemed like a good plan, but then, that's what they said about