Depending upon the strength of the coolers, sounds like a reasonable idea. J/24''s use coolers for a step going below, why not a bridgedeck on your boat? We had a similar setup with diesel jerrycans for a transatlantic trip we took, and it worked well. Wooden battens were installed on the cockpit sole for the containers to fit into and be lashed to. A teak board (held up by battens at the ends) was fitted between the seats over the top of the containers for more solid footing. That might not be necessary in your case, or desirable, if you want easy access to the cooler!