We have "double" towed since 1993, first with a Jayco 215SD for 18 years and the last five years with a Jayco HT 26.5 RLS. In both cases we had a professionally installed hitch attached to the frame. This last time, 2012, the welder also reinforced the frame from the rear to toward the axles. Our current boat, Crestliner Super Hawk 1900, weighs 3,800# full of fishing gear and gas. Weighed it yesterday on the way to the lake. Just make sure you get a good welder and you'll be fine. Our last job cost right at $500, but that also included the wiring for the plug for the boat lights.