I think the tubing is probably your best bet. Try to copy the hinges that you will find on a few cars with butterfly doors. Usually for butterfly doors you would have two contact points but with an H2 you'll only be able to use one I think so you're gonna have to make it very solid.
Butterfly are the kind you're actually talking about since a Hummer cannot even have Lambo doors (
http://www.statikdesign.com/scratchb...ody/doors.html). I plan on working on some in the next few weeks so i'll make sure to post.