[Toad]

That setup looks absolutely sweet Toad.. (wipes drool from mouth)

How does the Helios compare with the viewfinder from a DSLR? I have the impression that you would feel less like "looking down a tunnel". Does it provide any magnification at all, or is it basically just a framing guide? By the way, is it a third party accessory?

It is primarily a framing device with negligible magnification and is a third party device made in Russia. It has 3 sets of bright lines for 35mm, 85mm and 135mm - the 35 marks are almost spot on the 20mm's field of view.