I am installing the overhead cabinets today. One difference is that I am bonding (and screwing) the oak framed cabinets to the shell to add stiffness. First I cut away the elephant hide insulation so that the framework is bonded Directly to the shell to add stiffness. The end of the cabinet is also screwed and glued to the bathroom wall. Here is the prep work.
This is what they look like with each bonded to the wall and ceiling and to each other as well. This is the first cabinet.
Here is what the driver's side looks like now.
Here is a snap of the street side.
I noticed that the walls and ceiling were stiffened a lot by adding the cabinets and bonding them as well. The cabinets are basically a 12" deep oak beam reinforcing the roof and walls horizontally and vertically. Bonding has made them a structural part of the rig (for better or worse!)
I used Polyurethane hy-bonding sealant and adhesive for the first cabinets. For the last ones I used high strength construction adhesive from Lowes.
The screws I used are aircraft 100* type B sheetmetal countersunk screws with large diameter washers to distribute the loads over moer fiberglass. When I installed each screw into its countersunk hole in the fiberglass I added a dollop of polyurethane Gorilla Glue to seal the hole and waterproof.
The holes were drilled to the minor size of the screw to gove full engagement of the threads without splitting the oak.
After the glue sets the screws are just along for the ride.