I rode with a guy that was touring with a set of rubbermade boxes roped to front and rear racks, with no panniers. He was riding out of New York, on his way to Vancouver, BC. I met him in Michigan's upper peninsula, and we toured together for about five days before our paths parted ways. His boxes were holding up very well when I met him, which was already many hundreds of miles into his tour. I never did get a chance to catch up with him and see how everything worked out. But it seems like the plastic boxes were working for him. I think they should work just fine for you too.