I have same situation with TechArt 18 Formula's on the front of wife's C4S.....the 18s are the winter fitment.
It bothered me at first.....less man 2mm.....but apparently it will be OK.
TechArt spokes won't be 'flexing'......but I was concerned about movement otherwise.

 

Brembo suggests 2mm of clearance. After I installed my Brembo setup on my Audi, I tested my street wheels and they were OK. I put on my track wheels and spun the drivers side. Put the passenger side on and drove off. Fifty yards later, pulled over to find that the passenger side wheel was bent. It peeled the paint off that side's caliper. Oops.

I LOL'd at Damons setup! That is tight.