If you're making one, I agree, the bigger diameter threaded bar you can find the better. Just my opinion, but I reckon it is best to have the adjuster part offset to one side, I think it will be less likely to buckle, the middle is the weak spot in my view.
This is especially true if using it on a 32-34 rear spring, as the diff gets in the way of a straight shot. The frame has to be extra strong, surround the diff, and the threaded part on one side has to be in a direct line between the spring eyes.
Sorry, no pics, but just some ideas.
Mart.
Mart.