I carried our 10' Kayak on our ladder with a "lawn chair rack" just as you explained for several years with no problems. We bow carry them on the trucks roof as the new FW has no ladder rack
Just make sure you are not blocking the tail light.
2008 GMC Sierra 3500 SLT DRW D/A 4x4 (Big All)
2006 Ford F350 PSD SRW King Ranch 4x4 (Henry) (Sold)
B&W Companion, 90 Aux Fuel Tank, Scan Gauge II, Curt f/m hitch, Swagman XC
2015 Forest River Sierra 360 PDEK
DW Diane, DS Michael, FB Draco and Sabian