...I think I'm going +15mm on all four corners. I'm worried about the rear rubbing, though...
Justifiably so. I'm running 15mm spacers at each corner and had significant rubbing in the rear, even with the fenders rolled. I could try and pull them, but I'd prefer to run 10mm in the back. With the fenders rolled, they don't cut into the tire. However, they still rub when significantly compressed.
Your experience will depend on several factors, including ride height, camber, tire sizes, rolled fenders, etc. For reference, my fenders are rolled, stock camber (no adjustability), stock tires and I'm running a set of lowering springs from Spool.