Making progress 165 fps 412 gn 24.9 ft pounds. My xbow Black TB just shot at its best. I keep shortening the relaxed length of Theraband. It went from 95,110, 127, to 165 fps as I shortened the rubber. It uses double Black per side 6" pulled to 24". I am satisfied with the speed. My next goal is to increase the arrow weight to 750 gn.