Hi Josh, I'm not certain about all your past purchases and future options, but here is what I have for sale:
Phase One P21 with 2,000 shots. Bought two years ago from Capture Integration. Paid $8500. Will take $6000.
Mamiya AFD with 35,55, 80, and 210. $1500 with lenses.
Long story short:
I Bought a Kapture Group Truewide, V mount on the back and Nikon 35mm mount with Copal #3 shutter on the lens side (Fantastic piece of gear) with a Kodak PRO Back Plus very recently. Found that if I worked with it that the pictures had promise, so bought a 85mm PC tilt/shift and really started to enjoy using it. The trouble came when I removed the IR filter and put a 720 filter in front of the lens yesterday in Prospect Park. Through this seemingly normal action I learned that removing the IR filter in a Kodak back can cause an internal spring to fry the imager in these backs, now just a black screen instead of a photo when I shoot , although all the menu options work and the back thinks it is taking a picture. (Yes lens cap is off, etc. it broke while shooting, literally took a shot then stopped. Charged battery, retried, still nothing. I also read that it costs more to fix them then to buy another one.)
So now am looking for another back for this setup. I believe that my options are another PRO Back Plus (has to be Plus to work with the cable I have) but I am not willing to pay much for it because I've seen how easy these things fall apart. I have all the cables/ accessories that I need, so would only need a back. Another (better) option that I am exploring is a Phase One P20 or P20+ in V mount. I would have to buy a cable from Kapture Group to make this work on the Truewide. Any larger Phase One backs will be considered at the right price, but the square backs are ideal for the 35mm lenses (using the entire imaging circle). I would consider another option such as a CFV back, but would have to figure out how to make it work with this camera prior to buying. I'm in Brooklyn, New York, and can make it anywhere in the area to meet up to do a deal , but I will also consider a long distance transaction if someone is well known to this forum. I am nacoma2525 on on the auction site for your reference.