Finally moved my GF inside to the mother-in-law suite. I’ve seen some Diy versions of the window vent, but why not employ my laser.
Cut from Home Depot Baltic Birch sheets measuring 2.77mm so the inside panel fits very snug in the outer panel. Also, use the quick disconnect dryer vent holder from Walmart for the hole. This was a very snug fit (used WD40 to make the vent slide in, but I’d maybe cut the hole very slightly larger next time). Didn’t measure how far it expands but I know it’s more than 40" as build.
I still have the CDR and DXF files if anyone needs them as well.
Full disclosure, I used my large 500x700mm laser to cut the pieces, but you could use the GF and just cut individual pieces.