I’ve got centaurs from three companies. Left to right, we have a Doll Chateau Ada, a Daisy Dayes Elise, and a Soom Smokey, with an iPhone 3GS for size.
Smokey’s back legs are strung over a bar of resin located in the front horse torso piece.
His rear legs sockets have locking ridges in them, and you can see the ball of the leg has two protruding bumps that fit into the ridges. You can also set the ridge just outside the socket - I can get him to rear (and stay that way) if I do that.
Elise’s legs are strung over a hook that is part of the front horse torso piece.
Her rear legs have a peg that can fit in one of three holes, to lock the joint in position. It’s less flexible into terms of posing, but she is very small, and this makes her very sturdy.
Ada is…okay I’m going to be honest, I’ve never seen another quadrupedal bjd strung like this. She is strung with a single piece of elastic, from her head to all four legs. Only her arms are on a separate string. From her back legs, the elastic loop splits with one half from each leg going down into a front leg, and the other half going up into the torso to her head.
Her back legs have no locks at all. She is the least stable stander of all three. In fact, I don’t even have her try to stand on the shelf. She sits. The ball of her leg does have multiple slits though, so her thigh can actually rotate into different orientations, unlike the other two centaurs.
This lets her splay her legs out to sit super adorably.
Hope this helps!
Maybe when I start putting my monster together I’ll try doing a hook inside the chest piece and link everything up to that instead of one in the head.