At some point a lighter arrow travelling faster will have the same KE as a heavier arrow going slower. There will be more KE retained down range from the heavier arrow but if you don't shoot that far with that heavier arrow you may not reap the benefits. You have to make trade offs and figure out what is best for your circumstance and be confident. I shoot a 403 grain arrow at 69# 280 fps. I think it is sort of middle of the road to light but not super light.