Orchard grass stubble height

I have been cutting at 4" and have been very pleased with this. My mower is down, but I've got a friends 474 to use.
Problem is the shoe cannot be adjusted to my preferred height. Only able to get the pin in the second hole, meaning 2nd to shortest cut height.
Not going to mess with the shoe as it's pretty thin.
I'm very reluctant to cut this low. Seems like regrowth is just as important for the final (3rd) cut going into fall.
Frost likely in 2-3 weeks.
Is this a good line of though?
My mower should be ready Friday and there's still a window.

Orchard grass stubble height