Not sure if that's the way those 4 post are designed but from that picture it appears that those rear posts are canted in at the top. Are the bottom plates bolted to the floor?
You're right, it does look canted in the photo but it's dead plumb. It does have holes in the foot plates to be anchored, I held off doing that till I had used it enough to be sure I liked the position in the shop. I've moved it twice playing with location and spacing. I think this will be the final version, so I can secure it to the floor. It's not necessary for a 4-post but living in earthquake country I like the idea of it being completely stationary.
