I know the OPer does not want to use a trailer but after using mine for almost 2 years now I don't find it that bad, never a problem at any of the campgrounds and long pull thru sites are great, it also takes away the wear and tear on flat towing a truck/car.
A enclosed double decker to match your RV can cost well above $35,000, some even cost $70,000 but I had mine custom built for $5000, it gets the job done.
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The boat lowers down by winch/pulley system and than the trailer becomes a boat trailer behind the Jeep..