buckkilla....changing to a lighter arrow will improve the speed but will not help the KE at all. The only two variables in the KE equation are mass and speed. If you decrease one to get the other you have a NET 0 change in KE.

KE = 1/2 x Arrow Weight(grains) x speed^2 x 451080

There were some very detailed and heated discussions about this exact issue over at eders last year. Without getting onto a deep discussion and talking bow efficency, which is a minimal change anyway, the KE a bow will generate is essentially the area under the draw force curve and is independent of the arrow weight. The only way to add to this area, thus increasing KE, is to increase draw weight or increase the draw length.

That being said, Duckmastor2 I think that you are really on the fringe edge of the KE required for most mech heads at 35 yards. Keep it to 25 and under and you should be OK.