I finally took the plunge this weekend and tear away my old sliding patio door and install a new French Patio door.

After tearing out the old sliding door, I found that my initial measure was a bit off for the rough opening. Now that I installed the new doors, there is a gap of over 1 inch between the prehung door frame and header on the top.

Does anyone have any good advice on how I should proceed to fill this gap? Should I cut up a piece of wood and put it between frame and the header, also should it be flush on the exterior or interior?

Thanks in advance,
-Pete