[cely]

I compress the sides of the nylon spacer without modification. That is, I don't make it into a split nut. Actually, the forces required are quite small because the wall of the spacer is fairly thin. I can achieve a tight fit with just two fingers. If you think about it, the internal threads in the spacer are only 0.010" or so, away from being a tight fit.

I never thought about end-to-end compression.

Ideas like that are why I like this forum.