Actually, in reply to the "smaller models" excuse, thats a bunch of bullexcrement really. I mean, yeah, the crouch animation IS smaller, but technically its still the same, I mean, sure your missing about a foot off of it, but in reality that foot never mattered in the old version, cause the hitbox is still the same. The old models used to be like this:
*************
*___________*
l l
l l
l l
l____________l
The *'s represent parts of the model that didnt count when a paintball was shot at it, so the paintball would just go through the shouders on up to the head. The build 15 models, They reach the top below the *'s, so therefore you just have better aim cause you know where to aim for.