All sound advice. The only thing I might add is that if you have the chance, support them on the bulkheads. You said you will use would racks to keep them off the ground; try to place the wood supports under the bulkheads, otherwise the hull may deform in the heat.
Life is short, Paddle often
'03 Chevy Astro w/ NP233C 4x4 electronic shift transfer case, 4-5" Overlandvans lift kit, 4:10's w/ Detroit Locker, Rancho 9000 adjustable shocks w/ in-dash remote & onboard air compressor, 255 70R16 AT's or 245/75 16 MT/Rs depending, GTRV pop top w/ sleeper, Carefree Awning, Gaucho couch, Coleman Fridge, and tons of Thule
2010 Gas Gas EC 450, 2005 Gas Gas FSE 450, plated