The satin is more for looks (cloudiness vs. clearness) so I may just clear coat everything. The stencil idea would be good. Satin finish the scale, throw the stencil on engrave, gold leaf and clear coat all with the same mask.
What I think I will do is when all is said and done, satin finish the lexan and gold leaf it and put it in my rotation (even if I'm not gonna keep it) and use it as much as I can to see how durable the leaf is. If its solid, great, if it isn't well, I'll have to find a solution then!