I asked the same question of an areospace engineer. He stood in front of me and performed a calculus equation in his head to determine the amount of forward movement of the limb tip. After much debate, he and I summised that if the limb tip goes an additional inch in front of the riser, the draw weight will increase 1" accordingly. If your bow draws 3# per inch, you SHOULD have an equivelent increase in draw weight. The fwd movement of the limb(unstrung) will greatly increase performance, assuming that it isn't already too far fwd(law of diminishing returns). Sorry if I got alittle deep, that last cup of coffee is kicking in!!!