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Yeah, I did end up noticing the date afterwards. Oh well! Actually, the air space is not really an air space; 2x4 walls, 1.5 inches away filled with 2x6 batt insulation. I just couldn't find 2x6 bluwood studs. And the foil face dura is slightly more permeable than 1" rigid XPS, with the 2 layers being slightly less than the 1" but, again, slightly more than the 2".
Overall, it should allow for a good capillary break (as well as thermal) while still not being totally impermeable. The r-22 insulation is likely a bit overkill but I didn't want to leave an air space! haha
And I did use a gasket under my bottom plate, even though they say I don't need one. Better safe than sorry really.