Right, I've established that. I know I need one of those spacers from MM w/the studs built in. I just need to know what size to get. They sell a few different sizes.
Loco, I'm not sure if you solved this or not, but I spoke to guy a while ago with a '98 Cobra who had 15x3.5 skinnies in the front. I asked him how he fit them, and he said he used a 30mm spacer and they fit perfect. I don't know what size would translate to adequate clearance on the fox since they're different cars, but that's a start for ya.
Have you tried asking MM about this? I figured they may have some knowledge on the subject since they deal with both road and drag racing and they sell spacers. They may know a proper size to use.