This fight is a catch 22 for Anderson.
If he KO's GSP with a knee as he shoots 1 minute into the fight, a portion of people will say Anderson was bigger and it somehow made a difference in the outcome.
I think the fight is fair as hell and the matchup is awesome. People say GSP is the best wrestler in all of MMA, so what shoulld 15-20lbs even matter. His opponents biggest weakness is wrestling.
We get to see Anderson vs. a wrestler who is well-rounded.
Anderson is in his late 30s and has to cut extra weight, which may drain him a bit. Those factors by themselves more than makes up for the disparity in size, in my opinion.