Ducted AC

Not really a foamie question, but the folks on this forum seem to be the mad engineers of the community so I thought I'd ask here. I'm still in the planning stages for my trailer, but my thought right now is that I'd to use a td and put a sleeping platform in the back of a minivan. We're a family of 4 and I love to save money by camping on road trips, but I hate setting up and taking down camp. I want a quick, all in one solution that's cheap, small enough to fit in an average parking lot and still gets 20+ mpg. So a camper/van is the best solution I can come up with.
Enough of that. I live in FL so I need AC. Putting it in the camper is easy enough, but I'd like to be able to duct some of that air into van at night. I figure I could use normal 4" flex ducting hooked into a window in the van. But I'm trying to figure out how to create a plenum from the window ac unit in the camper that can balance the pressure for the two locations. Has anyone done this/have any ideas? Thanks!
Enough of that. I live in FL so I need AC. Putting it in the camper is easy enough, but I'd like to be able to duct some of that air into van at night. I figure I could use normal 4" flex ducting hooked into a window in the van. But I'm trying to figure out how to create a plenum from the window ac unit in the camper that can balance the pressure for the two locations. Has anyone done this/have any ideas? Thanks!