probably in the glue line or the wood right next to it.
An explanation similar to one of the theories behind perry reflex? I have always hoped to understand this better.
Consider the compression on the belly for a moment.
1. If one were to slice off a lam from the belly surface of an untillered bow, one could expect the lam to be just as stiff as any other lam sawn from the stave it came from.
2. if one were to slice off a lam from the belly surface of a bow that has been tillered and shot in, but shows no apparent set. one might expect the lam to be not as stiff as the lam above, but not necessarily deformed.
3. If one were to slice off a lam from the belly surface of a bow that has had the reflex "pulled out", I think one would find a lam that is permanently deformed and would take some effort to straighten. The rest of the bow might return to its glued in reflex profile.