I decided to give Bryce's idea a shot as grinding the casting flash off my calipers comes with less risk than boring out the wheels' hub seats by hand. Mine didn't look exactly gnarly, but there was definitely additional material from the casting which seamed (pun intended) unnecessary:
Before and after:
Before and after:
It's pretty clean. I even smoothed the grinding into the seam as it goes over the top and under the bottom of the caliper bracket. With some paint, you'd never know any work was done at all. Considering Mickey's still under warranty, some paint would probably be a good idea. I test fit the wheels with the 5 mm spacer and it worked (thanks Bryce)! The clearance is super tight, perhaps 1.5 mm, but they spin freely:
-- top of the bracket
-- at the middle of the bracket
-- bottom of the bracket
-- bottom viewed from underneath
I know most companies recommend 3-4 mm caliper clearance, but I scoured the old internets for minimum clearance and the vast majority of non-corporate advice is, "if it clears, it clears". There's certainly a larger safety margin with greater clearance, providing companies lawsuit protection with their clearance recommendation. I may be touting my ignoring here, but I feel like if my wheels flexed enough to make contact with the caliper, the lead up to that consequence would be more grave than the caliper clearance. Granted, it wouldn't help matters in a worst-case scenario.
It's been snowing since last night and having done this work yesterday, I put on my wheels this morning and took Mickey out for a cautious test drive, taking dips and bumps and such and listening/feeling for any grinding or vibration. It was solid and the Michelin Premier A/S tires gave me virtually more grip on snow and ice than my worn Ecopias provided on dry pavement. I then drove 27ish miles with no issues. I'm still a little nervous about the clearance and may eventually install full-length threaded wheel studs and use 7 mm spacers, but I'm satisfied for now. It was a hard decision, but I don't regret it. I need to give Mickey a wash and sort out an issue with one of the center caps before I take full car photos, but here's the final look installed: