I'd mount them straight so as to utilize the tops of the ammo cans to add more "luggage" space.

The loops on my tops are cheap Stainless Steel cabinet pull handles, and the fit the "rosette" welds on the tops.

I used 1/4" shaft collars as spacers due to the diagonal brace bars.

They are water proof, but if you are using the OEM leather bag mounts you might want to put some split tubing to isolate any rattles.
