sometimes I wonder if the reflex that is seen when a bow gets thinned, is a result of the most recently grown sapwood acting different from the older wood. I don't know if the older wood towards the belly could be considered heartwood or not, but it might be "seasoned" different from the ring just under the bark. If the whole bow is made from what was always on the upper side of the tree, then it would it not all be tension wood?
I use the term "seasoned" very loosely here, as I do not know a better word, although I guess it is possible that interior wood might season somehow, even if the tree has not yet been cut down. I am told it is dead, but still wet, and on it's way to becoming heartwood.
what ever the state of the belly, the new sapwood seems to be contracting. Perhaps it is just a difference in the way
the newest wood dries?