I also drilled the various control cable holes in the firewall today. This was quite nerve wracking as I imagined myself drilling in the wrong spot. I studied the plans very carefully, then measured and marked the hole locations with a black sharpie pen. Before drilling I measured again, then again, and I think I may have then measured again. I think I was stalling.
Anyway, with liberal amounts of beolube on my drill bits I drilled pilot holes before then reaming out to the correct sizes with a stepped bit. This seemed to work well. I now have the firewall holes for the throttle, mixture control, propellor control, and alternate air, as well as an access hole for the nose wheel attachement. I left the cabin heat hole for now as this needs to be enlarged to 2", and I don't have a suitable hole cutter.
Laying out the control cable holes on the firewall
Drilling the stainless steel firewall was a bit nerve wracking. I think I measured four times!
