Our Scamp had no cabinets to attach to, so here's what I did:
I marked on the ensolite where the shelves/cabinets would go, and cut a strip out along each mark about 1/2 inch wide, cleaning to bare
fiberglass.
I bought a 100 ft coil of black rubber 3/8 inch air compressor hose and cut to length for gluing to the bare
fiberglass.
I roughed up the surface of the hose well on the gluing surface with a bench grinder.
I used polyurethane glue and held everything in place with duct tape until the glue dried.
This provided a support system for the shelves to hang on. Shelves were made of thin ply and screwed into the rubber hose. Hose is on the inside of cabinets and top side of shelves, so isn't visible.
Problems I had:
1. Duct tape doesn't stick well in cold-rainy weather to the plastic covered ensolite insulation.
2. Polyurethane glue foams up to fill in space, which is good, but the excess needs to be cleaned up before it gets too hard.
3. It took a lot of time.
What I would do if I had to do it again:
About a month after I was into this project, some smart fellow, at least smarter than me, posted a large shelf setup using those wire shelf setups you can get at Home Depot. It went clear across and I recall it attached to the tops of the window frames. For a place to stow sleeping bags and pillows, it looked like a real winner.
Good luck.
Loren