Originally Posted by Spanik
It's a Sinar Zoom back. Can do 6x4.5, 6x6, 6x7, 6x9 and 6x12. I thought of coupling it to a Fuji SWD 75 but I have no idea for focussing. But the Mamiya Press lenses do have a helix build-in so that might be a better option. Doesn't surprise me there is some vignetting, they were intended for 6x9. Maybe the ones for the Polaroid version might be better, they do have a larger image circle IIRC.
Can your Sinar Zoom switch between 645, 6x7, 6x9 and 6x12 mid-roll? Or is each roll devoted to a single size? I could of course work to develop a back to fit the Zoom but it would take some time and I'd need an example of one to work with, iterate on etc.
The Mamiya lenses for the Polaroid 600SE do have a larger image circle because they were designed to cover the pack film (FP3000 and FP100 which are sadly no longer made). The three lenses designed for the Polaroid were the 75mm, 127mm and the 150mm. The 75mm covers the 6x12 and 4x5 fully. The 150mm vignettes on both (I've tested it). I've yet to try the 127mm but I suspect vignetting.
Re: Your Fuji SWC 75 - I've been thinking about building a lens cone that takes a Technika lens board and just sets it @ infinity. The majority of the shots are at infinity anyway. Oh how I'd love to get the Schneider 47mm and set it at infinity... mmmmmmmm...
Of course, having a helicoid is really useful as you can imagine. There are some 4x5 lens helicoids on the bay but I'd bet they are shoddy construction (aluminum).