Window4U - Thanks for your last response re: the expander header.
Now I have some insulation questions -
If my windows come 1/4" narrower than my rough opening, I should have a gap of 1/8" or less on each side. I read somewhere (this forum?) that gaps of 1/8" do not need to be insulated. The Norandex guy said to put loose insulation in the gap.
I've also read the discussion on non-expanding foam vs. fiberglass. What's your recomendation on the 1/8" gaps?
The height should come in at 1/2" less that the rough opening. If I raise the window to eliminate the need for the expander header, how should I insulate the top and bottom gaps?