I 've often heard the refrain 'I'm too big to be a climber'. This is too simplistic, since it doesn't take into consideration the field you're riding against. For example, I'm sure I can find a 6'5", 200 lb guy that can beat all the regional Category 3's and 4's, so I don't think that those guys can use that reasoning.
On the other hand, there is no 6'5", 200 lb guy that can beat all the very small guys that win on the world moutain stages. So if you're riding the Tour then you could say 'I'm too big to be a climber'.
So you're left with the continuum in the middle. Where in that continuum can the excuse no longer be used. I think that even the regional p1/2 races aren't fast enough to exclude big guys. How big is Barry Wicks for example, anyone know? He won Pescadero in '07 when I raced the p1/2s. Now Pescadero is not a pure climber's race by any means, but still, that guy is big. Nate English is not a small guys either and he kills the climbs. How big is Nate?