Guided a friend through two hickory board bows off the same board . Both long bows. in fact , the second was a copy of the first . The first was built in the winter (dry) 40#@28" .The second ,built in the spring (humid) 30#@ 28" The second took twice the set that the first did. Both built very slowly with lots of exercising of the limbs.(he babied them far more than I have the patience for) Many bows have been made from Pick axe handles and I don't think much regard was given to heart or sapwood. Usually quite hard to tell the difference ( colour is NOT an indicator on hickory,infact sometimes it downright lies) That dark colour can travel drunkenly back and forth across several anual rings. If it's got straight grain ,............. make a bow! Seems silly to back a wood that you use to back other more questionable woods, doesn't it? Making sure it's dry is the key to little set from the few I've had experience with. Looking forward to seeing the results!