On our Jayco Finch we can carry up to 4 adult bikes on the roof on racks running left to right that i have made that are similar to the Jayco racks but made out of 40x 40mm tube and a bit of angle and utilising bike mounting blocks bolted to the front rail. Basic concept being remove front wheel ,and place front bike fork onto the skewer on the mounting blocks and the rear wheel drops into a slot,between the 2 rear rails formed out of 20x20mm angle running front to back,throw a rubber tie down strap on each bike and away we go. The front wheels get put in camper or back of Prado,has worked well for us only thing is you need to remove the bikes before winding up roof.