Wow Robert, your details have paid off!!!
Have you had the chance to test on something wider than 9'?
If so, was it as simple as moving the BG lights to 5' or 6' out?
Also, can't tell from the pics - how large is the deflector and is it formed or flat? If you could take a pic of it mounted that would be great.
Thanks for describing the setup - I've had issues with off paper background shadow reflections on tileboard. This seems like a great way to hot up the BG outside of the frame.
Based on the current placement and readings I'm getting I don't think I'd have any trouble making this exact setup work for an 11 or 12' background. Pulling the light out might be necessary to make sure all corners and edges are being lit correctly. At a 12' width I might be inclined to angle the lights in carefully but you also have to be careful doing that because now the edge will be hot and you want to keep that at the edge and out of frame for any shots you'll be taking.
The Elinchrom deflector set comes with a silver and gold deflector. They are convex and have a pebbled surface. The Mini measures just under 5" in diameter.