I've laminated the cabin side using 16mm foam so it was thick enough to rebate the windows later. Having the windows fitting near flush would look so much better than them sitting proud of the side.
I've also continued on with the 16mm foam for the cabin top.
The pics show the foam in place. I hope to get to laminating it in the next day or so as I'm looking forward to fitting bulkheads. I may take some time out to further upgrade my vacuum table for the laminating of the bulkheads. It works well but an upgrade should give me a better duty cycle of the vac pump on/off.