I have my nuts sprung together one quarter ton. I hold the X screw in tension, Y and Z I crush angular contact bearings together. Everything is one quarter ton and feels glorious.

I sprung my Roland mini-mill to 200 lbf, I don't have a magic formula, I just use whatever seems right.

Do you have a way to inject oil in to the nuts or do you depend on that grease? I started fitting narrow bore nylon tube to carry oil but one of the push fit connectors didn't fit and I wanted to play cutting stuff so I left it out. I think I have to strip back and finish the job. Gravity feed is traditional but would that need wider bore piping? Such fun.

For a moment I was worried that I might have put you off with talk of backlash. Glad to see you back.