Here is a link to a thread with A-B-A testing of full wheel covers:
http://ecomodder.com/forum/showthrea...-6-a-4368.html
I noticed the bumps on the rim between the spokes. They look like an excellent attachment point for the covers if you drill & tap them for screws. It would look a little more hot roddy too.
The rear wheel arches on the XA are going to be difficult to close up. After giving the arches on my XA the scrutinizing squint, I'm inclined to make the rear skirts over a stressed skeleton frame made from light gauge aluminum flat stock. That is the only way I can see to fill the whole arch due to the curvature.