got this idea when just focusing on getting my capacity as high as possible, but what if after a certain capacity you and other contestants can get full enough to become immobile, leaving them at the mercy of others.
if friendly they might help you deflate enough to move, otherwise they'll either leave you until the next boom room or inflate you more.
could also have them comment or tease on the predicament as they pass by / enter the room.
this would make it risky getting too full and immobilzing yourself or getting hit by an item that pushes you over that edge.