Discussions like this always leave me wondering if there is any configuration of woman who can consistently find clothes that fit off the rack and just what that woman might look like.

As for sizing, I just pretend the letters mean something else:

L for Lovely
M for aMazing (or Monstrous depending on how the sizes run and if it fits or not)

XL that fits after you have lost weight might mean that item is for a person who is Ex-Large (i.e. formerly large)