Captain,

Yes he did not diet correctly, but that still makes him a very large man at 200lbs+
Your argument that Shields is not a big WW seems implausible as you yourself say that he added size to fight opponents at a higher weight class.

I think it is testament to how good Henderson was that he remained among the top 5 in the world before he fought Shields, but in actuality the Henderson that fought Shields was a mere shadow of the Henderson that fought in Pride. Like his old stablemate Couture, Dan has achieved a lot and had amazing longevity, but he is at the tail end of his career.

I don't know at all about GSP at 185. I really don't know what to expect there.