tandem on a roof top

I'm trying to put my newly used tandem island on my 11 feet high x 18 feet long truck camper, for a fishing trip to Florida from Quebec. This will avoid me to tow for such a long distance, which will be great.
Any smart ideeas you can share for how can it be done? Amas are light but the central kayak is pretty heavy
thank you in advance

I'd be curious of the relative gas mileage hit on towing vs. rooftop. Rooftop will add much more aero drag than towing I'd think. My gas mileage barely suffers when I tow my TI since the whole rig, trailer and all, weighs under 500 pounds.

On the subject of aerodynamics, I reckon an AI or a TI is going to do very little in terms of drag - as long as it's pointing fore/aft on the roof. The components are all pretty aero/hydrodynamic in shape.

I've taken my TI on my rooftop for many 1,000s of kilometres, and can never detect a difference in drag or subsequent fuel usage.

Mind you, I drive a Land Rover Defender, so aerodynamics are not it's strong point at the best of times.

In terms of getting it up that high - I easily roof mount my TI (and unload) by myself, my rack is 3.2 metres high, 11 feet high is apparently 3.35 metres, so probably high enough that - unless you are very tall - you may have difficulty getting it up that high without some sort of assistance system.

Will the roof support the load? How many times do you plan to unload/load the boat? How do you plan to get the durn thing that high?
You may find the trailer is not that bad an option. We have done it both ways, kept extra straps, tires and a hub with greased bearings in a spares box to ward off evil spirits. Went without a problem. If you do decide to put it on the roof consider getting a cheap aluminum ladder and screwing some pipe onto the rungs to support the hull.
Safe travels!

I really don't want to tow I'm happy with my park everywhere truck camper doN,t want to tow 3000 kms... to Florida
Yes the roof is rock solid is a Bigfoot fibrglass truck camper but the basement model which is higher,
I mesured 11 feet from the ground,
thanks in advance

Maybe mount some cleats on the side of the camper to hold down the straps. Also buy some of those "hood loops" for canoes and use a V shaped strap at the front and rear. Cross bars will dent the hull even if well padded, so to support the hull you can try 2x 10-12feet x 2inch PVC pipes in the grooves (you'll have to unscrew the venturi drains or cut out a hole for them). Or an inflatable sleeping pad or SUP. Or the Hobie cradles if you can get them lined up right, some people have mounted the cradles indirectly to an alumimum ladder instead of the roof.

found something on youtube
https://www.youtube.com/watch?v=dgxodOMpWgc

I liked the ideea of the V pole so probably I'll try a V sliding pole in and out over the roof to side the roof and down with a winch
thank you guys