Thanks, Max. Or should I say Sherlock? Add some grey to that diner window reflection and, by George, you've got it! 
Wish I had time to actually experiment with these ideas but for now I'm just thinking/dreaming and trying to find time around weekend schoolwork. There's a flaw in my thinking about using that plastic I found today for the stained glass. It's likely fine as a solid color upper transom pane. But if I want to suggest the outlines of the actual stained glass shown in my photos, then painting, ink, or fine cutting is still required to avoid adding unwanted thickness. Ah well ... That's were the thinner gel or cellophane would work better.
TRRR
