I am installing 2 side by side double hung windows and wish to bump them out by 8". The 8" walls on either side will be solid. I would like some suggestions on how to frame the bump out. The total R. O. is 72' by 56". I live in MA so insulation would be important. I am thinking of using hangers and extending 8" long 2x6 from the existing wall as the base, then covering with 3/4 plywood. Appreciate any advice.