remember that you will likely never get to what your bow IBO speed is. I.E. Mathews sayin Monster will shoot 354fps. It just ain't ganna happen. That IBO speed is with the absolute ideal conditions and are still probably inflated ontop of that. All bow manufactures do it by the way. When an arrow strikes a deer its not about speed or weight. Its the comination of the two. This is why you have guys that buy really fast bows (i'll point the finger at myself) and then shoot FMJ arrows that are heavy as a hickory limb. The only thing that matters is the kinetic energy the arrow has when it strikes the deer. Yes if you shoot lighter arrows then you will have less drop at 30-40 yards but you will be really hurting your killing power at that distance too. Its the same reason crossbows are not recommened past 40-50 yards. Yes they can still accuratly shoot that far and yes they can kill a deer at that distance but you won't be causing the same internal trauma when the arrow hit. I know this really doesn't help but it explains a little bit why the bow show might have set you up with heavy arrows.