"for every inch of draw length over 28" add about 10lbs to the draw weight to estimate your speed equivilent."
Longer arrows are heavier just because of the extra inches. And they have to be stiffer, which also adds weight. That's why so many of us long draw shooters went to overdraws on compounds in the 80's; to shoot shorter, lighter arrows and bump up speed. The statement is not technically wrong. It's just not generally correct.
Or something like that.[8D]