That's really an old thread :smile:
Oddly enough, meanwhile, there are adapters for almost everything.
I have now plenty of them, including those which I searched for when I started this thread.
The reason for loosing infinity focus is that Nikon has a larger registry distance than virtually all other camera brands. I mostly use these adapters to adapt lenses for macro use. Recently, I even managed to find solutions to reverse-mount an EL-Nikkor 75/4 on my D3 and on a Novoflex bellows, respectively. The EL-Nikkor has a 40.5mm filter thread, so I needed altogether two adapters, one step-down ring and the BR-2a to be able to use it on both combinations.
There are special adapters with an additional lens built in that allow you to gain infinity focus but I have never tried those and thus do not know if it has some adverse effect on image quality.
Cheers