I was talking to the salesguy at the local Norandex/Reynolds dealer about installing the Simonton windows I just ordered.
He said that if the upper stop and inside trim extend down far enough to cover the top of the replacement window, then I don't need to use the expander header. All I need to do is caulk the exterior around the stop, insulate the gap at the top and install the interior trim. He added that since the expander is wider than the window, it actually makes it harder to reinstall the interior trim and get the reveal right.
If that's all true, would it make sense to *insure* that the upper stop covers the frame by adding a strip of wood under the window to raise it up just a little?
I installed one replacement window years ago and I notched the interior side stops and ripped a little off the upper interior to account for the expander. It seems to make sense to eliminate the expander if at all possible.