At 155 I'm never going to doubt that he'll be in shape and have a solid gas tank but even now he looks just a little soft and looks like he could easily fight at 145. If you go to his website you'll even see videos of him eating hamburgers the size of his head just to try to get up in weight.

Even with a solid gas tank I see Penn running into some serious trouble since GSP sets a aggressive pace and gets more dangerous as time passes by. Combine that with the fact that he has the excellent strength and technique in wrestling that means anybody with a good gas tank or not will be worn down by the second or third round.

P.S. There's no way that Florian or Huerta will ever beat Penn in his current state, not even by a fluke punch or whatever. Florian is only a gatekeeper for the division and Huerta is still at least three or four more legit fights away from even becoming a contender.

The only person I see giving Penn problems at LW is Gilbert Melendez if he worked on his striking and focus. He's got a Liddell-esque ability to pop up from the bottom of a mount, great strength and wrestling to match too.