I got most of the window plug built last night, I thought I had enough material, but was fooled by a partial sheet of Durock® tile backer. So I'll have to wait for the weekend to do a run to the supply store and grab a sheet.
Here's the overall design of the window plug;
The handles are a necessity! This thing weighs a ton and once it press fits into the window space, there's no way to pull it back out again without the handles. Ask me how I know.
When I cut the inner plywood piece, I left a 1/4" gap all the way around as that would allow the felt to fill in and squish for a tight seal. The tile backer board is inboard of the plywood by 1/2" and seated on a bedding of GreenGlue.
Tonight the plan is to bring in some Roxul and start cutting things up to lay into corners! Here's a few sketches from Mike Sommer, the designer of the space.
and here is how to cut the insulation