Bucket.....
You're figuring this out too quickly
Clue:
Radius of Gyration and Moment of Inertia...is smaller
Don't bother looking it up in the little yellow book....
Here I'll save you the effort:
Radius of Gyration def:
The distance(radius) from an axis of rotation to where the Mass of an object(The club) would have to be concentrated to create the same moment of inertia of the entire object about that axis: meassured in units of length or expressed as meters in SI; a scalar quantity
- Biomechanics of Sport and Exercise 2nd edition, Peter M. McGinnis,p.394
Take a baseball bat and swing it from the handle...now flip it around a swing it from it's barrell...the overall mass of the bat is the same however the concentration or distribution of its mass is different thus affecting it's moment of inertia..which is the difference of what you felt swing the bat from either end...This is major reason why Mac sets-up the way he does ...
Lower hands brings in this distribution of mass along the adjustable radius where as raised hands moves this distribution of mass further out and its moment of inertia....Affecting the Moment Arm....