There are variations in the size of windscreens, in addition to the shape of the mounting stanchions which are well documented in Chris Gould’s guide.
The earliest cars seem to have a glass height at the very centre of the screen of about 205mm/8″.
The windscreen through the middle cars seems to become slightly lower, 197-200mm, or 7 7/8″(-ish).
Chris Gould’s book refers to a photo of a late, 1937, cars having a higher section. This screen (below) is thought to come from an early Nippy but is 8.5″ glass/10.5″ screen height:
Can you check and add dimensions to support or alter the hypothesis? There must be variation in how screens are assembled, but plainly the differences seen are not wholly due to this.
Dimensions – examples found:
1933: glass height 204mm (8″); frame 257.7mm (10 1/8″)
1935: glass height 200mm (7 7/8″); frame 250mm (9 13/16″ ish).
1935 LHD glass height 197mm; frame 245mm
1936: glass height 195 mm; frame 240mm.
mid 1936: glass height 200mm/frame height 250mm
late Nippy: glass height 197mm (7 3/4″); frame 245mm (9 5/8″)
tallest seen (red car above): glass height 216mm (8.5″); frame 267mm (10.5″)
This folding screen (below) on a 1936 car is of similar dimension the late Nippy above; 7 3/4″ and 9 3/4″
The overall height from the base of the side support to the underside of the comma/hood fork clasp bit 17 3/4″ (452.5mm) – does yours differ from this?