Welp, here's my medium-to-big-fat saggers model. Some usage notes off the top of my head:

• Some checkpoints work better than others.

• You can go above 1.0 if you want to get saggier.

• It does clothed and nude.

• Trigger words are technically "small breasts", "medium breasts", and "large breasts", but you can use superlatives too like "huge" for slightly different results.

• Age can affect sag.

• Repeating the trigger sometimes works better than emphasizing it.

• It can alter backgrounds and faces. You can use adetailer or an inpainting approach to deal with it.

• You can try to specify ?????? size. Not sure how well that works though.

• If ??????? are being finnicky, specify them in the prompt and/or inpaint.

HUGE thanks to Murky for training advice.