I wanted to carry a small kayak along with my Tandem Island on the trailer. So I came up with a PVC structure to fit atop the TI to carry that kayak. The main idea is 4 cutoff PVC tees that rest on the crossbars and a frame that rests on those tees and allows the mast to fit beneath. Then I use the Hobie strap and some bungees or other tie downs to hold the small kayak in place. I have not tested it over long distances but it has worked well over several shorter (10-20 mile) trips.