Just stumbled across a big fail (hard to spot) 🙂 First we begin with the IS-3:
The grey spots are 170 mm:
And now, the grey ones are 110 mm:
Behind these 110 mm spots, there is a hole in the armor (0 mm). You can get penetrating shots right there.
IS-5:
The 102 mm spot has no armor behind! Next to those thin areas are some 201 mm plates.
IS-4:
🙂
