The original Mary Poppins, had relatively small knockers since it would make it hard for her to become buoyant & fly off on her umbrella whilst anchored down by 10 pounds of knockers. Also Marys wardrobe only allotted her a meager B cup at the Warner Brothers facility.
Now the sequel that's a whole different story.
Its called, Marys Poppin out.
Instead of spending all there production money on special effects they just inflated Mary with helium so she could float around effortlessy, they also had to design a special bra, since most are made to hold the mammary up, whereas these had to hold em down.
Hope this helps Rack, kinda surprised you didn't know this