I'm thinking of putting one on.  I know CJ's never had them, but I think stopping the side to side action would help me from cracking the frame again.  As anyone ever seen one in the after market or am I going to have to custom make this?

Yup.  When you have a large lift, hydraulic steering, big tires, you tend to put more stress on stock designs that the engineers at Jeep weren't expecting.  My frame cracked right at the mount for the leaf springs.  So instead of concentrating all this force at the spring mounts, I could spread it between the spring mounts and another point on the frame.  At least thats what I'm thinking.  

I know its not uncommon on trucks with leaf springs and a large lift, and I know YJ's have them.  I was just wondering if there was an aftermarket one for CJ's.

Good points….  I don't have that much travel, its leaf springs and its a CJ.  It is SOA, and yes, I do use the hydraulic steering in some non traditional ways.  The steering did take away some of the stress because it pushes on the axle itself, but when I get in some situations as you suggest it does put a load on it.  I thought about shear but the way the crack formed it looks like side load.  Plus, when my suspension flexes I have plenty of swing left in the shackle to accommodate the longer springs.  Cut, box and brace, and I'll keep an eye on it.  Just looking into ways to keep it from happening again.