In case anyone’s interested, here’s that whole part with my custom support structure. This example is much more complex than what I’d expect Preform to generate, but it gives an idea of the utility. It just takes care of the spots that would require internal supports (and some other problematic areas); the rest of the scaffolding is generated in Preform. Most of the touchpoints are around 0.1mm, with a few larger ones up to 0.3mm, and it printed perfectly.
This is after the supports were removed but no other cleanup. There would have been potmarks had I used normal internal supports.
Sorry for the lack of scale. The whole model is about 3.5cm tall (pretty small!) and those layer lines you see are 50μm.
EDIT: One in Grey, still on supports (though some of the ≤0.15mm ones detached in the wash):
