Good eye! With only 10 triangles to spare and an entire extra material slot, I think the move is to separate the lens onto its own material, and to make that material alpha blend with ‘show back face’ option checked. I did this to all 3.
Yes this strategy is working fine in this case! I’m approving the collection right now! @DOCTORdripp
Often the best move is to select only the faces you need double sided > duplicate them > flip normals for the duplicated faces. This way you don’t need to add extra materials and the duplicated faces follow the skin weights if the base mesh has already been weighted.