i wouldn't drill out OEM brackets. if you have to, i'd get some aftermarket ones. much cheaper and probably easier to drill through. guess it's too late though.

on a sidenote, do you have the Karbon Haus Mugen or OEM rep?

 

Double Sided CF OEM Rep. I've used the replica OEM hardware, and there is a subtle difference. The OEM hardware pops up (fully locked) at the end, whereas the replica OEM hardware does not. I'm only drilling the top half of the brackets, so I'll buy a replacement set (Thanks S2KVee) from the link.

 

Replica tops in general no matter how well they are made take more time to adjust for proper fitment.