Shields had to cut so much because he didn't diet down to a proper weight first. He hadn't fought at 170 since October of 2008, he'd gotten bigger to fight bigger guys. He and GSP will be similarly sized come fight time.

And I know Henderson had all sorts of problems going into that fight, but that's not Shields' fault, Hendo was still ranked top 3-5 at 185 when they fought, and I'd be willing to bet that GSP embarrasses Shields worse than Shields did Hendo.

GSP will be fine at 185, if he ever makes the move. The only guys I forsee him having issue with are Chael (much bigger, at least as good of a wrestler), Palhares (bigger, BJJ monster, but I'd still pick st. Pierre), Silva (much bigger, great stand up, good off his back), Okami (much bigger, at least as good of a wrestler, different style due to Judo base), and Hendo (POWER and wrestling). He'll easily be top 5 at MW.