I play with USA on and kept the default value at 1.33.
Here is a thread explaining how USA works and why it’s not a bad idea to keep it at 1.33, even if you obviously play on a different ratio.
Important Guide to Uniform Soldier Aiming.
Anyway, seems like an never ending debate from the research I did.
Although, I’m really comfortable with my current settings, I might give 1.78 a shot.