My barrels are currently hung using cable grips which works pretty well. I am unhappy with the attachment of the cable gripper to the underside of the bus. They are held on using a single nut on each end of the gripper. In my opinion that's not secure enough.
I'd been idly thinking about other solutions, most of which involved a lot of welding. As I happened to be in Tractor Supply today to get two aluminum strips to replace some I messed up yesterday, I noticed a very interesting ring hanger.
Apparently it's good for 400lbs. It seems to take a 1/4 inch bolt so I can put two nuts on each of 4 bolts then, having tightened the bolts, I can gently weld the nuts to the thread. If I leave the existing attachments and add just two chains per barrel then I can be sure my barrels will not shift. Both attachment systems should work. It's worth the extra cost for the extra peace of mind.