Thank you to everyone who responded. Just as an update:
We put it in the rear bay and it did just fit. We still added supports - it is really solid. We used sikaflex to seal it (got it at home depot in the concrete isle). Everything has cured and is sitting well. We didn't seal the inside of the van (we were worried about moisture somehow getting in and using the roof supports as a bridge) so hopefully that is a totally unfounded fear.
It was an easy install, but just slow going and stressful.
We put it in the rear bay and it did just fit. We still added supports - it is really solid. We used sikaflex to seal it (got it at home depot in the concrete isle). Everything has cured and is sitting well. We didn't seal the inside of the van (we were worried about moisture somehow getting in and using the roof supports as a bridge) so hopefully that is a totally unfounded fear.
It was an easy install, but just slow going and stressful.