> The varnish is the finishing layer that is on top. That layer is also, fwiw, about 3-5 mils most of the time

Are you saying the varnish is that thick, or the layer the varnish is on is that thick?

Painting on a 3-5mm thick layer of varnish sounds like a lot of coats.

The below link is from someone who makes violins and they make the top 2.7-2.8mm total thickness.

https://www.violincellomaker.com/2021/03/17/how-the-thicknes...

Edit: rereading your comment makes me think that you’re saying the total top thickness is usually 3-5mm.