Out of curiosity, I just measured my rear window, 250 mm just a little under 10 inches. Also 250 mm in centre of drivers door window. 90 mm chop according to me, which is 3&1/2 inches. Perhaps someone will measure one that is stock height in the centre of both side windows and rear window, from the steel part of the body, not including the rubber moulding as a datum. Then @3w Hank will have some accurate figures to work from.
As on Hot Rod Ron’s coupe my rear side window is also at 250 mm or ca 10”. I think std is ca 13”. I checked std coupe from under dropplist to body contour at door and std was 462 mm or 18.18”, and my was 387 mm or 15.23”, so that is ca 3”. I will keep my old 3” chopp ( as body guy don't like cut it up ) but from 2-4 inch is all Ok but for a more hard look it can be 5-5.5” but under that it start feels odd ( my way see it ) -One thing I do notice some feel better to look at and no matter if it was 2 or 5 inch and it can be pictures, color, fenders or not and if roof was edge shopped, leand back or not A pillars etc.