As for your 'peep hole' lens. Back in about 1965 I used one on my Retina Reflex. You can't just use the peep hole as it doesn't project a real image. It's made to look at with your eye. I mounted it on a lens cap and put it on the front of the lens. With a 50mm lens the circle is pretty small. It worked pretty good with the 135mm lens. I later got a Kenko Fisheye adapter which worked much better.