I can imagine it now.
Incoming autism for my write idea;
A guy is so amped up letting himself be shrunken and stuffed between a pair of a woman's breasts.
He's stuffed in there and the oppressive heat, nauseousness from movement, and general claustrophobia, start to get to him, and overtime everything only gets worse.
She starts sweating which he finds gross, the smell starts to become kind of strong, he's feeling more and more nauseous from a combination of movement, heat, and stink, at this point he's not enjoying the experience at all. He's becoming more and more anxious from all of it.
Eventually he's freed from her breasts and is only met with mockery when he says hes had enough, and shortly thereafter stuffed back in.
TL;DR; I wish I were talented enough to right a good GTS breast smother short story.