Is there any legitimate reason why it's NOT a big goofy person with minor prosthetics? If it has "herniating tendons" like a human, perhaps it's because... it IS human? The stride, the proportions, the movements all look WAY too human to be anything but. Folks making comparisons to movie costumes are missing the boat. Those have to allow for being taken on and off and re-used many times over multiple takes and filming over the course of months. And they have to be worn by people who can actually act, most of whom are regular-sized with regular body proportions.
Whether in 1967 or today, if I wanted to make a one-and-done bigfoot hoax film I'd do the following:
1) Go into the hills and find the biggest, goofiest, most inbred looking hillbilly possible
2) Offer him/her $500 to don a costume and walk away with an angry face when I show up and start filming
3) If I did step 1 correctly, this is already a hairy MF'er to start with, but on top of and around that, I'd glue more hair onto their skin and try to mimic the patterns I'd seen in pics of gorillas n' shit
4) Pull women's nylons over their face, legs and arms and glue more hair on top of that.
5) If they have long ass Jon Jones arms, we're good. If not, hang prosthetic monkey hands (that I got from my uncle Skeeter who works at the Halloween costume shop) from their natural hands to extend the arms.
6) Grab my camera and try not to laugh
