Hey, I ended up using mapping instead of RC on this one.
I sent a small scene to Paul and can send it to you if you still want.
You should contact Martin if you want the latest build, I'm guessing he'd be glad to send it to you directly
Project finished for now, so I stopped testing this out, but I suspect it had something to do with the "Vray instancing" within the XMap settings...
Thanks again for trying to help out!