This thread made me go out and experiment with my D5xl.
I just got the machine about 6 months ago and had only done medium format so far. However, I still shoot 35mm and so this got me wondering. I mean, I know that alot of people have done 35mm with a D, and mine came with a "well used" 35mm carrier, so ...
Here's what I found.
I mounted my 63mm El Nikkor, and lo and behold, couldn't crank it high enough; until: I remembered that there is a second adjustment for the bellows. You can adjust the lens stage of the bellows up and down separate from the focusing knob. Mine has a lever "behind" the bellows that allows the lens stage to be adjusted. It also has a scale, and when I moved it up to "14"; voila! No problem with 7x10, 10x14, and larger.
I haven't tried it with a 50mm lens, but I bet the solution is the same.
Good luck with this.
Cheers.
David