As far as I'm aware the tri top is about as short as they come, regardless of size fitting.
Mine cuts me off about half way down my ribs, whereas for someone people it seems to stop around their belly button, that may be because of the length of my torso or just general wear I'm not sure.
Having said that though, I've worn the tri top on various Holidays in 40 degrees, and it's no less comfortable than a sports bra.
It has only one layer of material on the back so it's way more breathable than a lot of binders, so I've never had the issue of over heating

Hope that helps somewhat!