When I was making holes on my back floorboard for my nitrous bottle bracket I would take the back end of a center punch and clampitt and some vice grips and heat the tip of it with my torch LOL and press it into the carpet..
Damn it! I still caught a snag when I put the drill in the hole and pulled out a strip! I have them by my shifter as well LOL I have to color them in with a dark marker to try and hide them.. I guess my advice is make the whole plenty big enough so the drill bit doesn't catch any of the ends..