Make sure that you get hub-centric wheel spacers which have a lip in the center that supports the wheel, and that you get longer wheel bolts to match the thickness of spacer that you use. I have been tracking with Porsches and BMW's for years with hub-centric spacers with no issues. Your wheel bearings may wear a little faster, but big deal - they are made to be replaced.
By the way, Brey-Krause just announced a new line of all hubcentric spacers (even the thinner ones):
R-5010 Hub-Centric Wheel Spacers
The weird thing is that their web site advertises them only for 911's. Does anybody know if these will these fit a 986?