Hmm... after converting the coat to OBJ (as I was going to send it to Gerard for testing), I decided to try a sim with the new coat. Much better results!!! Still a bit of lumpiness but not nearly so much! ?

Here's what I can say that is different about the older and newer coats. With the older coat I was relying on using Carrara's "smoothing" tool within its modeller, to subdivide the mesh before sending to VWD, whereas the converted coat was imported without the need for using that smoothing. The resulting mesh (which was in effect subdivided in the conversion to OBJ) worked much nicer in VWD with minimal lumps.

The collision character has also been reliant on the smoothing to subdivide the mesh, but it doesn't seem to affect the simulation, as far as I can tell.

I still have to deal with a few poke-throughs and some areas where the inside of the coat poked through, but those are issues for another day..

Yay! ?

Thank you Smaker1 and Gerard for your attention while I tried to work this out!