Modelling UVs for interactive cloth (2019 HDRP)

I've been trying to get the default cloth to work on a rigged character using 2019.2.0f1. I've discovered;

1) If I export the cloth mesh from Blender without UVs, it works fine. This leads me to think the problem is entirely UV related (but, of course, I can't texture the mesh..).

2) If I add UVs (I've tried mirroring, scaling, different unwraps, etc. - they change which vertices are displaced, but I can't find a way to unwrap without the bug), the bounds/mesh bug out as below in editor view:

The bounds can be corrected in the editor view with 'update when offscreen', but the problem carries over to runtime, making the cloth a complete mess (the physics seems to use the displaced vertices as shown).

Does anyone know the 'correct' way to unwrap a rigged object for cloth - or is it simply broken in the current version? Failing that, any understanding of how UVs interact with the Cloth component would be a help. Whilst there are many tutorials out there on making a ball roll through a sheet, there seem to be very few on the full pipeline of modelling and unwrapping rigged cloth.