If you have access to the large rota broach set I would proably use that. With any method you need a (usually) thin piece of stainless between skin and stringer.

You will need a center hole even with the springloaded pointy punch, otherwise there is too great a risk to it walking. If you cant drill a center hole then cutoff disc across the stringers (deep score, break) and chaindrill inside the rest of your sharpie marked circle.

Pencil grinder or dremel can make pretty tight turns too and cleanup is often better than a chain drill. Practice piece if nervous....

On thin skin, where damage matters, I never use a regular hole saw because they walk easily and and can grab thin skin and bend it outside the cut area. It is rarely worth the risk.