Looks like you're doing a super job! If I remember correctly, as I measure the space between my fingers here, the vision blocks on that cupola are around 2.5 inches high by 5.5 wide. Thickness is about 3 or 3.5 inches (anybody who can supply exact measurements please do! ... Robert).
The green tint comes from the layering of glass and isn't from an actual tinting as such, so it is very light. Yours looks very good! The only thing I'd mention (and I'm being VERY VERY picky here) is the hold down 'tacks' for the frames, are they PE? On the real vehicle, all those little rivets are slotted screws for retaining the vision block frame. There is also a plate inside at the bottom of the block held in by three screws to keep it from sliding out, but you barely notice it.
I'll try to post a photo of the inside I have with the blocks missing for you on Ron's site.
Regards,
Ron
PS Shermans WERE too thin skinned, why apologize for stating a fact?