Cheesey- The crack is in the collar between the 2 set screws. I never really cared for having the rod further out on the boom personally and there are other ways to accomplish that which are more robust. I believe cannon used to make a metal collar which are better. But the dual axis bases are way better but pricey.
I would say unless you know how to remedy the crack or reinforce it I would not use as is.
hope this helps. Let me know if you are still wanting them.