Advice on A/C in Cargo Area

I'm wanting to put A/C in the Cargo Area of my Sprinter.. We have a 2,000 watt Generator with inverter.. We did the window unit in the Back Door Last Year.. Well I should say 2 of them.. They didn't keep the Van Cool.. We have insulated our Van and use a Espar D-4 in the Winter..But Im sure being on the road and all the rough roads and miles had a lot to do with going through the window units., I would like to know what some of the rest of you have tried.. Thanks..

I'm toying with an idea to temporarily use A/C in my Sprinter. I've looked at the portable Frigidaire units for $300, which use an exhaust vent for the warm air, I believe. I have various reasons for not installing a roof unit. I'm interested in discussing ideas and experiences with you/those here who have been down the path or expect to this Summer.