I've seen some of the local cognoscenti speak of balance point measured from the trigger. Makes a ton of sense to me.

The "how and what" of shotgun dynamics is irresistable. My brother's a real engineer (as apposed to a sanitary or systems engineer )and we BS'ed late one night about how to non-destructively measure sectional weights of guns - looking for the weight distribution that makes a sweet swinging gun. Something that could be lined up next to Rocketman's inertia measuring machine at the table. He thought the only way to do would be a liquid displacement in a very big graduated cylinder. We couldn't come up with a liquid that would be acceptable to gunmen. Scotch would foul up the oil finishes.