Both the 23mm and 28mm rodenstock's are awesome, but they are very limited by their 70mm image circle. This comes into play worse on a 1:1 Phase Back, like the 65+, or IQ160, 180. You can get max about 5mm of horizontal shift. At 3mm you will hit the penumbra (inner edge of the image circle) this creates a lighter white curving band around the corners. Past 5mm and you hit a some form of a blocking disc placed in the lens by Rodenstock. This disc creates a hard black vignette and makes this portion of image the non-usable. You can get just a bit more in rise and fall maybe 6 to 7mm. Depending on the image, the penumbra may or may not effect your shot. If it's blue sky it will, where as trees, rocks, water etc. it won't be noticeable.
The other issue of these lenses is filters. I personally feel that the physical CF is needed as the vignetting at the corners is pretty harsh. The CF is 72mm to 95mm outer. You can get away with about 1 95mm filter before you cause a edge vignetting. In my work I tend to use both a ND and CL-PL, which makes the 28mm Rodenstock tricky. I have moved to using large sheet filters for this lens. Optically it's truly an amazing lens as is the 23mm, but it's a bit more tricky to work with. BTW, if you don't use the physical CF, you have a outer filter diameter of 72mm and you can still only get one filter on before you start to see vignetting.
This is why the 32mm Rodenstock is IMO the better lens. 90mm IC, shifting to 16mm and it's possible to use it without the physical CF. The 32mm is hampered by cost, and it's a bit heavy and can have issues with the Copal shutter where the lens gets out of adjustment.
I am also curious how well the 17mm Canon is holding up on a full 12mm shift on the IQ180. I have the newer Canon 24 TS-E and it's a great lens but tends to show a bit of softness towards the corners on full shift and will also show considerable light fall off on a full shift, enough that I will often times take a LCC frame with it.