I've heard turners claim on a number of occasions that all that really matters when it comes to tenon size is the amount of contact that the jaws are able to make with the wood. That is, that diameter doesn't matter. Is this really true?
Is there no benefit to a larger diameter tenon once the jaws are contacting the wood as much as they ever will?
Under this assumption, if I'm going to use my Oneway Stronghold Number 2 jaws to hold a tenon for my bowl, I might as well always use a tenon that is just barely above their minimum external gripping capacity (2"). A tenon that is 2.2" in diameter would be just as effective and have just as much holding power as one that is 3.3" in diameter--as long as either is being held with the number 2 jaws, the maximum contact between the jaws and the tenon is already reached at the minimum diameter. Likewise, if I'm going to instead use my number 3 jaws, there's no reason to allow the tenon to be more than around 3 7/8", even though the maximum external gripping capacity is 4 1/2".
I've always calculated my tenon size as 30% the diameter of the bowl, and assumed that there was some sort of inertia benefit to having a larger-diameter tenon. What do you think?
Is it true that for a particular size of chuck jaws, a tenon that is just above the minimum external capacity is just as good as one that is close to the max?