Must say, not sure I agree fully...
A "perfect fit" harness is sometimes not good
Meaning, if it fits so it sits just right, without load, or just with a "test" load in a rope, it might NOT work when under load on the water for longer time.
I've tried and had so many harnesses during the years, and even those that was sitting PERFECT on me, was not bullseye when kiting for many hours, and led to light pain
The stress points, and the stiffness of different parts of the harness, will be deciding - and that is not always possible to know in advance IMO, not even if a custom build
It is really such a fine balance, and not that easy - and if one finds a harness that suits - stay with it forever, or as long as possible.