Don't put too much weight on my advice, because I'm pretty new at this. But, here's a couple of thoughts:

-- The range you quoted of up to 0.12" is just about 1/8 (0.125"). So you don't have to thin much. I've been using 1/8 wood and now acrylic. I don't concentrate on thinning.
-- If you are going to round the scales like we commonly see, then you will create the illusion of much thinner scales. Its because of the thinner edges.
-- You will thin them some just from sanding out the scratches.

I'll be interested in hearing how the epoxy resin works out. Don't forget some pictures.