RS4 B7 rear brakes to B5 RS4

[dhali]

right guys have been reading brooners guide on the brake upgrade on his B5 RS4. Now the rear ones had to have the hole redrilled to 12mm in the upright as the B7 caliper carriers take a 12mm bolt instead of the 10mm one used by the B5.
Is there anything on the market that would reduce the 12mm hole to 10mm on the carrier itself? ie i was thinking of helicoils but have since been told these wont work.