I'm no expert, but my better hackberry bows are coming from bigger trees.
BUT I'm not one to go indescriminately sawin down trees. I've been fortunate to have a big one blow over recently.
It had a trunk about 16 to 18 inches... a real nice smooth sapwood back. The blanks i've saved ---not a knot in sight.
one benefit i've noticed is not as much propellering as happens from the younger trees who are always twisting around like kids.
Its nice to shoot a bow made from a tree whose rings shared your summers and winters with you.
just looking at its rings brings back memories.