Many thanks to you folks for checking out my website. What makes this simple and cheap is that you shop around for a lens shell that's already been gutted of it's glass, I've got a Mamiya 645Pro-TL and was able to buy two lens-shells(80mm/150mm) sold as 'for parts', for next to nothing, apart from the diopters/magnifiers I experimented with, I found that the lens cells in various junk lenses/projection lenses, had casings that were threaded(so you you could unscrew them out of the lens) which fit roughly to the filter accessory thread of the lens shell and to a number of step up/down rings.
The lens shells already provide you w/a helicoid for focusing, and the step up/down rings can be used between the lens cells and the front of the lens to get the glass closer to/farther away from the film plane to give you a usable image. You'll have to play w/it.
Going through the junk lense/projection lenses, I unscrewed the front and back cells, and fitted them to the lens shells to see if they were close enough to fit the 58mm and 67mm threads of the shells, and/or my various step up/down rings, and then looked through the lens, not scientific, but a lot of fun.
You owe it yourself to check out the photographer who was my inspiration for trying this, a Russian photographer by the name of Georgi Rozov, I found his website one day by typing in 'contemporary Russian photographers' into my computer, go to his website @ http://www.rozov.ru and better yet, if you don't speak Russian go here http://www.rozov.ru/index.php?p=galery&category=19 which is a page on his website where all the work was done w/a 'Monocle'. Go down to the eight row of pictures, the center picture which is the portrait of a woman in heavy 'greasepaint' type make-up, was the one that made me decide to start the 'Cyclops' project. The stuff on this page is ABSOLUTELY DYNAMITE!!!
'Monocles' are 'old hat' to Russian photographers, which is what they call a lens shell they've mated to a single element lens, they done this for years in both 35mm and MF. I had one single contact w/Georgi Rozov, let him know of my project, he was flattered that it was him who inspired me, and he responded, and I'm sure you'll enjoy his work.
Looking for leftover lens shells 'for part's' and junk lenses/projection lenses is DIRT CHEAP, there's some drudgery, but if you're not in hurry, you will sooner or later come up w/something interesting.