My XV Merlin shoots a conservative IBO of 320fps with an 8 inch brace height and extrapolating its efficiency to determine what a power stroke 2inches longer for a 6inch brace height or 3 inches longer for a 5 it would shoot 350-360 fps. In 22 inches of power stroke it already has the same efficiency as the speed bows so why is the draw so smooth with no aggressive roll over? I would love to see an XV with a new riser that put the same set up two inches foward to give a 6 inch brace, it would then have a 24 inch power stroke. All the super speed bows don't seem more efficient just longer stroked with short BH. Anyone know of a speed bow that is efficiency driven? I would like to see one more efficient than the XV.