At least with V4WM you can use the JCM fixes... like Prototype Letterwork's Real Arm's product... and get the best of both worlds.

Which, as Paloth says, is really what is really required... especially, as I understand it, if the mesh is not wholly designed for weight mapping.

Of course the Gen5 mesh is supposed to be wholly designed for weight mapping... and I do reckon in general I'm seeing a slightly better elbow shape, in bending, than in Eric's example. I am not sure to be honest if Genesis does have JCMs that are simply hidden... or what?

I am generally, at present, manually posing Genesis though, rather than applying any poses from my library... I don't know if that is making a difference to my results?