Yea well, Seahawk fans have been tearing out the bottom of drink cups for many years, I saw and did myself way back in the King Dome era.Noise makers are against NFL protocol, even "homemade" ones like you are describing. It's in the fan conduct agreement, you can actually get removed from the game and potentially lose your seats because of it.
Selling popcorn in a container of xyz size violates no rules.