There is a good article in the latest Deer & Deer Hunting Mag about this topic about trying to gain a few FPS. One thing too many peopledo not think aboutis that you may have 50 ft-lb at the bow but down range it drops off dramatically and the rule of thumb is 50 ft-lb at the deer not at your bow and you shouldn't rely just on KE.

For every 5 grains you loose about 1 fps. So, if people would just go to 100 gr tips they'd only loose about4-6 fps at the bow but not as much down range since a lighter arrow slows down faster then a heavier one.