I've spent a good deal of time researching the Patterson-Gimlin account. I am rather convinced it is authentic, but hesitate to fully commit to believing it's real. The shoulder width and proportions of the arms are convincing, as well as the shin rise and vertical foot when striding. Below is a bio-mechanical expert's analysis (Dmitri Donskoy, used to train Russian Olympians).
If it's a hoax, it's extraordinarily well done, especially for it's time - as the suit, if it is one, is above and beyond the day's top cinematic quality. Not only that, but how they established the realistic shoulder width and arm proportions defies understanding, as well as the shin rise.
The only characteristic of the subject that seems somewhat off to me, is the region where the ass meets the leg. It's abruptly bulbous and looks somewhat like it could be a suit to me there, where the torso is separate and is pulled up over the leg, or slipped into.
But as far as the rear end is concerned, Brown University Biologist Christine Janis did have this to say,
"It's not a logical argument to claim that because Bigfoot looks like no known ape that it can't be any type of unknown ape. Should another ape (besides ourselves) have evolved the habitual bipedal walking, then they would also have likely evolved methods of stabilizing the mass of the trunk over the hips, such as enlarging the gluteus maximus muscles as in humans, which is what gives us our larger buttocks. Note that the members of the horse family, which habitually fight by standing on the hind legs, have larger gluteal muscles than other hoofed mammals, and correspondingly larger, more rounded buttocks. A Bigfoot with a big rear end is actually a predictable likelihood rather than an impossibility."
Lastly, Heironimus is a fraud as is Phillip Morris. Neither of them has any proof that they played a role in the video, yet skeptics seem to willingly take them at their words on this topic, while scoffing at the reliability of eyewitness accounts, which is ironic.