I have an 03' XKR Convertible and have 18" Milan wheels that are 8.5x18 F ET33 and 9x18 ET35 rear. After reading a bunch of god forum posts I decided to try a set of 15mm H&R offset adapters in the rear. Figured if I wanted more, I'd move them up front and get 25mm for the rear. After fitting them, I think I'm going to stick with this first attempt. They might look better with more - but I hadn't thought of how the brakes look far back from the wheel. A matter of preference, and not terrible, but it's certainly noticeable even at 15mm.

I like it though. Subtle but noticeable difference - in the rear where it's most needed. More than I expected from 15mm. The BBS Milan's had deep cutouts between holes where the extended studs can easily "hide" so no material removal reqd.

pics show right side stock, left side with 15mm offset installed. Then the brake closeup shows one stock, one with the 15mm offset.

Right rear stock

Left rear 15mm offset

Right rear stock

Left rear 15mm offset

Right rear stock

Left rear 15mm offset

Front brake clearance stock

Rear brake clearance 15mm offset.

 

That looks really good. They can look rather lost in the rear arch as standard.