The current world broadhead flight record is held by a 100# hickory, very dry, stiff handled flatbow, it was about 64" long, 2" wide. The shooter was short drawing it a bit. Jeremia Rutherford who pased away a few years ago, way too young. I would have guessed the bow to be about 60# by looking at it.
Marlon Torres AKA "Heavy Bows" owns a 250# 72" long hickory flatbow with stiff handle, it is a beast.