There should not be that much movement. Are the windows metal? those WILL absorb exterior heat and "move".

Either way, it should not be enough to affect an inside mount shade.

If you want outside? Use the sill width as the outside dimension.....but you seem to have enough inside casing to mount inside and leave a gap behind the shade, and how much gap will depend the variety you select.

Jan - thanks for the guide on the outside mount guideline w the sill. My concern w mvmt is the foundation of this house and the slope it's on. This house was empty for 3 yrs so probably messed up the foundation with not being cared for in our heat.. There were/are still some issues potentially despite some foundation repairs and I just want to make sure I can get to the interior of this window to caulk any future cracks up at the top that would now be behind the mounted shade. Yes the windows are metal.

I need to look through some samples photos. For some reason interior mount w no curtains or trim work seems plain to me and I like more character.

Nothing prevents you from doing curtain panels on an iron rod, over an INSIDE mounted shade........and still mount the shade forward enough to get a hand back there.

The issue is probably the QUALITY of the window and the install, more than anything else. As I said......especially if a metal frame window....cheap version!!!

These were anything BUT cheap! When the sun heats them up on a sub zero day? You can hear the POP!!! as the sun goes behind a cloud...as they move!!

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