Hey, I wasn't expecting to see you here
I sort of understand half of what you are saying there. For whatever reason, those two mirror lenses have mounts that allow them to be mounted to any SLR without much work, and that includes Nikon. Somehow I was convinced that Nikon's flange distance was at the extreme that didn't allow mounting any other lens without either losing infinity or adding glass to fix the problem; Apparently, that's correct only when standard mounts are in question. I've heard of T-mount and seen "adaptall" lenses/adapters/whatever but never paid much attention because 1) I had what I wanted available in Nikkor lineup and 2) previous sentence.
I'll definitely look into it. This M42 thing is developing into a mini-saga now. Who would have thought. Everything should be easy and simple (haha).
I'll have to grab one of my Nikons tomorrow to reload, then I'll come back to this. It's fun though, I like this M42 thing.
EDIT: Ah, I got it now. A little bit (more) of reading never hurt anybody. So F mount does not have the largest flange distance as I previously thought.