Guys - Is a size 12 too big?

Anyone can look bad at any size if it's not their natural size (same thing going down sizes), but if you are saying 12 is ideal for you, then I'm sure it is! Most women famous for being beautiful do not have realistic or proportional bodies. They are either skinny girls with implants, or they are just the very rare "freak of nature" with huge for a small frame (see Victoria's Secret girls). I personally prefer a girl that is more naturally-proportioned, and I think a lot of guys would agree with me. All the three girls you listed are damn hot, so if you look remotely like any of them, you should be pretty happy!