I decided to see if my 15" SS wheels would fit over the rear disc calipers today....
Nope, of course they don't.

I knew it might be close and was hoping through some grinding I might be able to manipulate them to work, but it isn't even close. The wheel won't even go onto the studs.
Guess it was a good thing I like the Billet Specialties on the car but I was really hoping it would work so I could switch back and forth. Especially on longer trips, like the Power Tour this summer.