This method is obvious but not helpful if the monitors are of a different
size. I want to run Excel on my Wide screen laptop, "below" my 4:3 monitor.
The stretching method either means I can't use all the widescreen or I lose
half of the title bar.

What's really required is two completely separate windows with their own
title bars. You can have this in Word and Outlook. Why not Excel and
Powerpoint where it would be much more useful!?