I have always focused wide open with the paper I am using under the peak device corrected for my eyes.
I want to see grain, sharp grain. I then close down two stops and work, I have never seen the reason for stopping down.
I have always used APO lenses and my film is always in glass, we check alignment periodically.
Seems to work for me over the years.
Please don't cloud the water here, as I appreciate the value of stopping down, but not checking focus at one stop down.