You can see the insulation I haveon the one wall in post above...foil, foam board...thats only on one wall right now and the roof has nothing.. The 10,000 btu unit will cool this down rel good, and even cycles out from time to time down here in laredo from 5 pm (after the sun starts to go down) out...from noon till sun down, its workin its tail off to just be comfortable,
and that is coolng the whole van...now once the rest ofthe van is insulated and the ceiling is in and the "curtain" between "my space" and the cargo area is up, then the 10,000 btu should do a really good job no matter where...but as with all of them, no matter what size...the hotter they get from the sun beating on them., the harder they have to work to cool...