Too bad it's not a Syncro Camper. Then you'd really have the ultimate fishing machine.
As for your question, maybe a cooler rack built to go into a trailer hitch?
Speaking from experience though, vertical 10 footers can be more then a little scary on some roadways. Vertical clearance can be a VERY serious issue.
I was going to mention that above 70 mph or so on windy days they start to sway in a mildly concerning way too, but in a Vanagon that's irrelevant...
