Thanks AB! That's a lot of good investigation and reporting.

Now it's my turn to question the validity of the prop you're using. Is this the Poser hi-res square? That is a two-sided prop that creates double and contradictory tension on the vertices, and a lot of problems in rendering. It should be deleted.

I have been using a cloth rectangle that I build myself in various ways. I do not get the anomalous edge behavior that you are seeing with my props. With extreme density I do see the corners fall a little faster than the rest, but everything flattens out immediately upon hitting the ground.

I have to get to work for a meeting but later I'll post some of my sheet props for all to use.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)