I did some 1/8” black acetal and tried doing a double pass at power 100 speed 30 and single at speed 15. Both worked well and I don’t see much difference in the cut quality. One thing that did stand out was that the double pass had a lot more white debris around the cut area similar to smoke stains on wood. I think this is because the debris can’t go out the back and has to come back through the top of the cut since it’s just a trough for the first part of a double pass cut.
I have some Delrin from laserbits but haven’t cut it yet. It’s a thin sheet. I’d like to get something a little thicker like yours. At least I have a place to start from. I’d like to make a seal/stamp sometime.
I’ve found the edges on acetal to be a bit melted so they’re somewhat rounded off as opposed to sharp right angles. Also, I think the picture you’re thinking of is the second one from double pass which I think was the back of the piece where it may have melted out of the pattern as opposed to the top where it melts into the pattern. The sheet was only 1/8" thick so the overhang aspect wasn’t very dramatic either way for me and works well. Definitely something to consider in the application of this material though.