...When I removed the original window, I had nothing left except the 2x4
studs that make up the frame. Then of course, you have a half inch of
plywood, and the siding.
The original window butted right up againt the aluminum siding. So when
I removed the original window, I needed to do something with the
siding, like put a j-channel all around the perimeter.
If I have the window sit entirely on the frame stud, then the sill of
the new window, with it's drain holes, hangs over the plywood -not