My Pastel Yellowbelly Jag takes a large rat without problem and it leaves almost no bump. He weighs around 2500 or 2700 ? I have to weigh him , but he is pretty big. My big female can also take larges without a problem (or a big bump).
A large rat from one supplier is smaller or larger then from another, though... I need to weigh one once.
Usually I feed all of my adults mediums, but he would stay in feed mode and go back to cruising within 3 days on one medium. So I bumped him to larges. That actually keeps him satisfied for at least 10 days so, sometimes I go 14. I actually do not stick to a extreme feeding schedule. The young ones, yes. The hatchlings get food every 5 days, Juvies 7. Adults sometimes 7, sometimes 10 days. Sometimes even 2 weeks. I have no set "feeding day".
But I do like them on rats, because as is I have to order it online and I don't want to complicate matters, since they all do so well on them.