If the trailer is taller than the van, are you sure the mast will clear the trailer? Maybe the mast should go on the trailer?

Bob Richards used to have a sweet rack on his pickup for his Seaspray. It extended out over the hood and tilted down for loading/unloading. It also kept the bed area clear so he could pull a fifth-wheel trailer.

That won't work with a van, of course. However I think just using manpower to get a boat on top of a van would be tricky because of the height of the van.

Can you get an endorsement to pull two trailers in California, or is that just a Nevada thing?