Kimbo weighed in at 235.5 for his fight with James Thompson and 234 for his fight with Tank Abbott. Both Thompson and Abbott are in the 260 range, so Kimbo was taking on a bigger man (although in Abbott's case the weight difference was all fat).
And as for Shamrock? He seems to be going into the fight worrying about how much smaller he is than Kimbo.
Shamrock said in a recent interview:
MMANews.com: What strengths do you see Kimbo having going into this fight?
Ken Shamrock: Well he's big man, he goes like 250lbs so he is big and powerful and he moves pretty well for a big guy and he throws big punches. He is pretty straight, although they are sometimes looping but they tend to find the mark and he has power behind them. He has some strengths that I have to watch out for and he is one of those guys that if you go in there and you are not sharp he will catch you.
MMANews.com: Have you been attempting to put on weight to counter his size?
Ken Shamrock: I've been trying dude. I think I'll be coming in at around 260lbs.
MMANews.com: 260lbs eh?
Ken Shamrock: In my dreams. [laughs]
MMANews.com: What do you plan on going in around?
Ken Shamrock: I'll be going in around my natural weight at 215lbs if I can. I'm around 212lbs right now so I'm trying to get up there.
Shamrock is overstating how big Kimbo is, but when you hear a fighter say he weighs 212 pounds a couple of weeks before his fight, you assume you're hearing from a light heavyweight who's going to cut seven pounds before the weigh-in.
In reality Shamrock, who weighed in at 220 for his last fight, is fighting at heavyweight even though he's tiny by heavyweight standards. That's another reason that hardly anyone gives Shamrock a chance to win this fight.