The Patterson-Gimlin Footage.

[Kurokage]

What convinces me is that if this is a suit, who would think to add boobs? "Patty" is swinging some C-D sized breasts. That's a weird detail to add if you're creating a hoax.

I've often thought that too. 
Who goes to the trouble of adding boobs? Back when it was filmed they would've tried to keep the image a little blurry and distant not knowing what would have been done to it in the future, so why boobs?