5x12 vintage cameras are fairly uncommon. The downside is that since there was no ANSI standard whatever with the ULF/panoramic cameras, if your 5x12 does not come with film holders, you're going to have the camera out of commission for an extended period of time while S&S or AWB makes new holders to match your camera. This is less a problem with vintage 7x17 cameras, because it seems that there are a lot more of them out there, and the holders are more standardized and more available. If you want to go with a modern 5x12, however, AWB and S&S make film holders on a scheduled basis to fit the Canham 5x12 back, so you are guaranteed a good fit. I shoot 5x12 and this is the route I went for my 5x12. I have the Canham back that fits on my 5x7 woodfield, and three matching AWB holders. The modern outfit was $3k for the back, bellows, and three holders. If you went with a classic 5x12, if you could find one, you'd be looking at similar money, plus a six month downtime while either your back was adapted or the film holders made to fit.