Anyone have great designs for a rock jack or rock crib corner post? Most of the ones I have seen are all tipped over and don't hold well.

If I understand what you want, the ones I've seen were made with 5 foot or so dia fence crib, filled with big rocks, and the post in the middle.

The high school ffa class here has been making them out of oil stem pipe. The up right pipe sticks down below the V shaped piece that you pile big rocks on. The V shaped part is made out of sucker rod, it must be about 1 inch rod with a rods angled to the top. The sucker rod on the V is spaced about 10 inches apart
Alot of our ground is really rocky

This is somewhat off the subject of the OP. I grew up in Kansas in the 1950s. There are litterly millions of limestone fence posts scattered around the state. Sometimes both sides of the road, for miles and miles, were lined with the limestone fence posts. Limestone was also used as a building material for many structures. A Wikipedia article is found at https://en.wikipedia.org/wiki/Fencepost_limestone. I haven't been to Kansas for many years so don't know if they are still standing.

The secret is stacking the rocks so they cant shift, 3 by 3 and alway pull from the far corner.

You can do some cool stuff with the Gabion baskets.

reverse engineer for cost effectiveness on your project

Potsdam, Ohio, about 64 miles West of here, has or had a lot of rock crib posts and a lot of mortared rock posts. They used round granite and the occasional quartz boulder. The posts have outlived the fences. I think the granite posts are pretty. A lot of houses in the area are faced with round granite too. Most of the posts are over 3 foot wide.

There's a few old stone posts south of London, Ohio too.

Keith