You can pretty much guarantee he's not over 180 lbs (in shape); he's probably closer to 175 lbs. I'm guessing he weighs 170 lbs or a touch over on fight night.
Think of it this way: He has GSP's upper body minus the legs.
But if he is a legit 5'9", it's hard to imagine him being anything short of 170 lbs.
"...I don't care whether you're happy, sad, scared or indifferent ...When my music hits those speakers, I will make that walk - and I will make it EVERY SINGLE TIME"