Converting to Electric Roof Lift?

If you're up for some custom fabrication like Notakwanon's awesome pneumatic system, I would recommend looking at the electric lifts used on boat engine hatches. They are slim, strong, and have a lot of travel. Two at $300 - $400 each wouidn't be super cheap but I think they would work great and they wouldn't have the problem of being stressed too hard at the beginning of their travel like the ones the campers come with. You'd just have to make nice mounts.

Here's an example: Link