24x is probably perfect for "F" class. I don't like objectives which are too large for a number of reasons.
First, I don't shoot"F" class at night so light gathering isn't an issue.
Second, I like to mount the scope as low as possible since it makes shooting the rifle more comfortable.
Third, a large objective bell hangs too much weight out ahead of the rings. Fourth, big objectives are, to my eye, ugly!
I have used 36x scopes on occasion since 1982 and actually don't like them as well as the 24x. The limited depth of field and limited field of view is a problem to me.
30mm tubes are nice because they yield greater adjustment range but, since the 300mm tubes are all attached to big objectives I stick with 1 inch tubes and live with it. Regards, Bill.