The problem is that Kelvin is a pretty good scrambler, and Chris (while great with TD's) isn't amazing at holding guys down. He's great at doing damage while on top, but because he really tries to do that his top control suffers. It's a trade off. He could adjust and be a bit more conservative to ensure he holds top position, but that would be a change for him and we haven't seen much to show us he's interested in doing that.
Think about it this way: Moose has been relatively easy to hold on his back during his career. King Mo did it, Jacare did it, even Machida did it. But Chris couldn't hold Moose down. And in the end it was Chris who got tired because he kept having to take Moose down again. A scenario like that with Kelvin isn't hard to imagine, and this is a 5 round fight. Even if Chris scores TD's early and the first 2 rounds look like the first round of Chris vs Moose, if he gets tired again because of it that still leaves 3 more rounds for Kelvin to take over.
Just something to think about. I won't be betting this fight big either way barring a GIANT move in the odds.