Dimpling/countersinking for #6 or #8 nut plate screw

I am building a Bearhawk 4 place, and have to install a bunch of nut plates, like a lot of aircraft. I have looked and searched everywhere else for info on dimpling and CSing for nut plates.

I know if the top skin is thin to dimple it. if the bottom substrate is thin, dimple it as well. If the bottom substrate is thick enough, CS it. But there is a big range in between where the substrate is too thick to dimple, but too thin to CS. Anything over .040 is too thick to dimple, but even a #6 screw dimple in the skin needs more than .060 skin the CS without blowing out the hole in the CS.

I have heard to use a #40 CS cutter in an installed #6 nut plate. Use the nut plate as a guide to over CS the subsrtate. Is this an acceptable practice? I thought creating a knife edge and/or oversize hole in the bottom of a hole was verboten. The application where I am doing this is cowling/instrument panel/boot cowl.

What is "best practice" for this. It has to come up a lot.

Thanks in advance for any info and advice.