We carry ours on Thule loop style carriers on the TV roof. They are simple and have worked reliably for about 8 years now.
But we did see a neat looking modification on a 5er last weekend. The kayaks were mounted vertically on the back of the unit. Looked pretty sturdy (not much whip/shake) but was impossible to tell exactly what the mount system was as we passed them; might have been using the ladder somehow. Maybe someone will know if it is a commercial mount?
2011 Jayco X19H (purchased 2015)
2008 Jayco 1007 PUP (purchased new, traded for the X19)
2012 Chev Traverse LT with TP