Originally posted by Lowell Goudge Heads are a different thing all together, I presently use monfretto ball heads, but may look at a panning head at some time. The issue with panning heads is I have found that when they are loose, you have one allignment and when you lock the allignment changes both in the vertical and horizontal, so I went away from them. ALso, they are no better than ball heads for long lenses, and in fact the number of different parts makes them more prone to high frequency vibrations than a ball head.
I do not disagree with anything that you have indicated. I am not referring to a panoramic head (i.e., Nodal Ninja, etc.), but rather where the panning base is located - below the ball or above the ball, on a "standard" ball head. If the panning base is below the ball, when you pan, you may not be panning horizontally around the true vertical but rather around the vertical axis as determined by the amount or "goodness" of "levelness" as determined by the legs. With the panning base above the ball, when you can adjust the ball for a true level, you have a much better - more true vertical axis to pan around in creation of a level horizontal plane.
So there are really no additional parts, just the order in which they are physically positioned or stacked up. If you are not able to reorder the "stack", then yes - you can add an additional panning base below the clamp, or swap the clamp assembly for a panning clamp assembly. It is all based on the design and manufacturer of the ballhead. Probably greater than 95% of the designs have the banning base at the bottom, with the rest either offering the ability to reorder the stacking of the unit (or inverting it), or offering the a panning clamp or another option.
Here is a link with several ball heads - the first is a ball head with the panning base below the ball, while the last 2 have the panning base above the ball (note - just looking for images that illustrated the concept)....
The main difference other than functionality, is that there is indeed a bit more mass higher on the ball head unit.