Hickory does make a great bow and adding sinew can add great performance. One problem I have with that combo is in high R/H areas that combo can change from a rocket launcher to a slug. Years ago I made a copy of Jay Massey's Medicine Bow, sinew backed hickory with a rawhide covering. When I made it it drew 56#@26". A month later it dropped to 45#@26" due to high humidity. I sent it to a friend in Colorado to play with and in a month out there the draw weight went up to almost 65#. The bow was sealed well with Tru-Oil and a good coat or two of poly. The bow shoots well at 45#, This bow even killed a doe with a stone pointed horseweed arrow in Connecticut and a turkey in Florida.
even well sealed the R/H at the time affected the draw weight of the bow.