Hi massivewire,
I perf cut vinyl+lam decals on our Roland SP-540V using Versaworks. I struggled a lot at first to get good results, but I found using a 60° blade (vs. a 45° blade) made a big difference. I cut at speed of 6cm/s. Knife depth (gf) depends on the specific materials used (as well as the sharpness/dullness of the blade I'm using that day), but I usually set the force to about 170gf - 220gf for the perf. For rectangular shaped decals, I often set up the file so that the perf line of 1 decal exactly overlaps the perf line of the next decal (so it cuts the same line twice). I'd rather have extra deep cuts, and have to pickup the decals off the floor, than trim by hand afterwards if the cut wasn't deep enough. Lastly, I do the decals in small batches, usually 3' of length or less. That way if the cut results aren't so great, I can tweak the perf cut settings for the next batch.