Yeah, it's kind of a genius play because the average joe will say "hey lookie here, texas scored 18 yesterday, I'll take the over", so you're right, the under is probably good.
The only sure thing is that there is no sure thing.
You should think about taking houston. I think I read somewhere that teams after being blown out by 10 runs or more win something like 75% of the time. Although Houston is pretty terrible on the offensive side so I don't know.
The only sure thing is that there is no sure thing.