Yeah that was the debate: unless you reduced the mass it would get increasingly painful/dangerous to use the smaller paintballs, but if you reduced the mass you also defied the point of doing it in the first place. Unless you could make very fragile shells it be pretty pointless. What WOULD be cool would be if you could make a fill that was solid in flight but became liquid when energy was exerted on it (like the opposite of that custard powder stuff in stab vests). Can't see that happening any time soon though