I put a 15'4" canoe on my TC's Maggie Rack.
Maggie RackI've also transported mountain bikes on the rack, but I had to twist their handlebars in order to get the bikes to lay flat. I have a plan to install a sewer hose holder up there, too. It'll keep my back up/extension sewer hose out of the way.
Give TopLine Manufacturing (Maggie Rack) a call. They have kits for longer than 4' side rails and 96" cross bars. Sometimes, the receptionist that answers the phone is a little ditsy, so put your patience hat on before dialing.
'13 F250XL SC gas 4x4 8', Camper & Plow packages, StableLoads, LT285/65R-18 Goodyear Wrangler A/T Adventure, 18x9 Ultra Motorsports "Phantom" wheels
'12 Wolf Creek 850 TC Coleman Polar Cub 9.2k A/C, 90 watt solar, dual propane & batteries, Maggie Rack