Just a few days ago I saw a frock coat with a generous slit down the back and tried to eyeball it to see whether it came out to rov pasuach. Close call. Then I stole glances at the wearer, both front and back, in search of rounded corners and didn't see any. So I was dan lekav zechus and assumed the slit went less than halfway up.
If I understood correctly, according to Pe'er Halacha you count the lapels as corners, so there are actually six, which means you'd have to round off at least three.
- Binyomin of Ben's Tallit Shop
