I would love to take the sawzall and put a good slice through it just so I could measure, but I'd hate to waste a caliper.

I spent a bit of time in the garage sorting through my shim collection. I have a dozen 1.5mm shims. Current plan:

Shave 1~2mm off the nub.
Lift the caliper off the mounts with a shim (1.5mm)
1/8" wheel spacer ... another 3mm

Should give me an easy 5mm of additional clearance without affecting offset near as much.

 

Actually...1.5mm shim between the caliper and the mount and 1mm off the top of that little nub and I clear my Speedlines. Not a lot of clearance, but there all the same. I need about a 2mm spacer to be comfy...maybe three. I think a 5mm wheel spacer would solve the whole situation.

 

Tried the other side today...5mm gives plenty of clearance for the caliper, unmodified. I had to stack a few shims on the lugs to find out...should tide me over until my spacers come in.