To protect the finish, use masking tape to cover area for gauges. Then do your lay-out on the tape, and drill through the tape. The tape will protect the finish during cutting. As for the hole saw, i'm not sure about carbon fiber, but fiberglass you want to drill through the front. The gel coat on front is easier to start drilling through, as the back has the glass mat closer to surface, so it has a rough texture that can snag on the hole saw.
DO NOT use a hole saw on your CF until you confirm with someone that has drilled CF (i have only done fiberglass). I'm just giving you an idea to keep the finish unscratched
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1970 T1 W/MassIVe 2913cc RAT/?EFI? w/direct fire (very soon) and 915 trans
1962 SC 1776cc SP 944NA brakes, 993 wheels
VKG