Unfortunately, it looks like I won't have a choice, unless I run the original axle (no chance) or get something so wide that the tires are going to hang out of the fenders like it's 1973.

I haven't measured, but there only seems to be about 8 inches from the frame rail to the outside edge of the wheel arch in the rear fender. I don't really like the idea of loosing trunk space, but with the humpback there's a little more room to play with, without giving up all my storage.