[MrFlippant]

Interesting on the fit of the collar, on the ones I have printed so far (6 off), the black PLA + (ESUN ePLA ST) is prone to swelling and the collars are a quite tight, the white is some old Creality PLA that came with a printer and this is slides off more easily but is still retained. 

Those variables are why I don't design a gap when I want a press-on fit like this uses. If someone's printer/material is causing it to not work, then it's the machine/material that needs tweaking, not the design. But, it's pretty common for designers to adjust the design of a thing to work on the their printer with whatever material they use, so I don't get bent about it. That new feature in PrusaSlicer (and I expect SuperSlicer as well) really made the adjustments super easy, whereas I used to have to import an STL, convert to solid, redraw the parts, extrude/cut as needed, export, and slice/print... now it's a couple clicks in the slicer. :) The one difference in the slicer is that the entire model scales, not just that specific tolerance area, so if I wanted to maintain everything else, I still have to edit the model. Fortunately, the original was large enough that the 60% version was still comfortable to use. :)