Those Agri-supply shanks are great. I found they are much better than the stock ones which were on my 7' Howse box blade. Those had slots in them instead of holes and I was bending and breaking them right at the slots. The holes on the Agri-Supply ones offer a stronger geometry, not having a built in weak point like the slotted ones. They are a pretty good deal too.
Here are the stock ones with the slots cut out. they are a little out of shape now.
When I re-modeled my box blade to accept the Agri-supply shanks I made it so they could extended 6" below the box when the box was level to the ground and the shanks were held by the top hole. Tilting the box blade forward I could down about 9", but with all the hard pan and rocks on my property, my 55 hp (8000lb fully loaded) tractor would lose traction, so it made no sense. Even so, I only made my hydraulic system travel 4", so I carried the shanks in the 2nd to the top hole. Otherwise they would always be 2" below the sides of the box.
I just re-ordered new shanks and got the 16" (3 hole) ones. They fit perfect using the top hole. Now they don't stick up above, and like I said, I really don't need to go much deeper. And they were under 10 bucks each. If I do need to rip deeper, I can tilt the box blade way forward and they go another 2" or 3" deeper anyway. That is about all the depth I need for what I want. In order to make them stronger and less prone to bending, I added supports 5/8" thick on the sides and back of the tube the shanks run through.
With these improvements, I have not bent or broken one of them, the supports and better shanks really helped.
A couple tips ... DO NOT make turns while ripping. This places lateral load on the shanks and they are only like 3/4" thick. Always pick up the box blade during a turn if you are ripping. For ripping hard pan and tough penetration, use weight on the box blade or make sure it is very heavy on its own like mine is now. For really had stuff, take several shanks out and use only 1 or 2 or 3 spread out. Then after that you can insert the rest of them and re-do that area to crumble up the chunks. Box blade the rest to level and smooth.