I built one for doing 4x5 and now I am going to build one for doing 5x7 for paper for my pinhole camera for WWPD. Pictures here:http://photo.net/black-and-white-pho...g-forum/00XrEp It is just for doing Black and White, I know others have built ones for doing color.
You could upsize this and do 5x7. http://www.btinternet.com/~g.a.patte...lfdevelop.html. I built one for doing single 4x5 and it only uses 6 ounces of solution. It did not cost as much as my rotary processor but the rotary will do 2 sheets at a time.