[nzwilliam]

Without looking at references that last photo looks suspiciously like a G model

+1

I'd put money on it that it's an early G model.

Some E models do seem to have it though, the Bf 109E-7/TROP in the photos here certainly does http://www.strijdbewijs.nl/top/p/me109.htm

As for the 109-F, perhaps you could make it a very fine/semi transparent line like on the early Emil photo Skunkmeister posted? It looks like overlapping glass to me. Probably slides open.