This variation is staggering. I can just finally fit into a 12 after getting a little below 150, and I'm 5'3". I started out at almost 190 in a tight 18. I don't think I look oddly proportioned but I do have a belly. In fact, I think I'm a smaller size standing up than sitting down because of how my belly bunches up!
Anyway, I've definitely had a different experience with sizing than most of you guys.