65 I just stuck a 3X on my 375H&H.
Other criteria is to own enough rifles that I can have a 3X on one,4X on a couple more,a 6X on another,and a variable on another. Then I grab whichever one seems most suitable at the time.
This avoids tough decisions.
There are some mounting systems that work well with a 4x33,Talley Lightweights among them.