5 gpp was put in there by the lawyers and the companies to protect the company. However, I'm not saying that means it's cool to just drop way down. I wouldn't go much below that weight though to be safe. Paul gives a good explanation of why. I've shot my bow at 75# 375 gr arrow and the vibration was no different than with an arrow 70 grains heavier with my Ally.

A friend that owned a shop had a guy that came in with a bow that the guy was shooting arrows that weighed something like 4 gpp with a 70# draw. He said every shot sounded like a dry fire but the bow didn't look harmed in any way.