I have a new method I am going to try. I have some headaches with my current method that I am sick of dealing with and I don't really want to discuss, and I am cautiously optimistic that my new method might produce equal or better results much faster.
I am going to buy some extension tubes for my Canon 5D Mark II DSL. This will allow me to do the macro photography that I need. I have a variety of lenses I can try to get the best results. Currently, I think I will use my 35mm F/1.4 lens because when combined with a 28 mm extension tube, it will give me 0.98 x magnification at a distance of 140 mm which would put it just out in front of the lens. I am not sure if it will focus that close though, so I will experiment once I get the tubes.
This is the general idea, but I will build my own rig with this concept:
http://www.johnamon.com/2010/08/how-to-copy-35mm-film-with-dslr-camera/
I am going to try using this as a back light. The brightness is adjustable. http://www.amazon.com/gp/product/B004TJ6JH6/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1
These are the tubes I will get: http://www.amazon.com/gp/product/B003Y60DZO/ref=oh_details_o00_s00_i01?ie=UTF8&psc=1
This is the wireless remote shutter I will get: http://www.amazon.com/gp/product/B0049HCSM8/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1
I did a test shot with my 135mm lens with a 1.4 and 2.0x extender on it handheld with my monitor showing a white page as a back light and it worked as a proof of concept.
The hardest part will be making the holder for the film to slide through. Until I know exactly how far from the lens it needs to be, I can't really plan for it. I am thinking I might be able to use a lens hood somehow but not sure.
Update: just had another idea for the mount. Most of my lenses have a 72mm filter size. I bought a 72-77mm step up ring. I can superglue this to a block of wood. I would cut a hole through the wood and mount my two 35mm film sliders from my scanner rig on both sides of the hole on the other side of the wood. Then I can just slide the film through the sliders and see the whole frame including the sprocket holes. I just need to get the depth right. If I can set the lens to F/22, then I get more depth of field which will help.