When filling up your stuffing, you would fill to 5000, as you typically do. However, it will pause for a second and let you leave, unless you stay and over fill to either 5500 or 6000 (idk which would be better for balancing). When you exede 5000 stuffing, your body looks overfilled, stuffing leaks out your zipper, and the teeth of you zipper do not lock together properly. You look more and more overfilled the more you are over the limit. It could even possibly slow your movement or limit what gadgets you could use. When you are overfilled, if you are hit with an item that deals knock back you drop a certain amount of stuffing (100-200).
This way, if you are building something, you could hold more stuffing to continue building longer. However, people could steal your stuffing if you are not careful, possibly creating vulture-like players who steal stuffing. Overfilling on stuffing could even work as a heath system in mini games, thus that when you lose all of your excess stuffing you lose the mini game. I feel this would be balanced because you do not have to overfill, meaning that you are not going to be attacked by people looking for stuffing. However if you do fill up, you risk people snatching all of your stuffing.