Update on the screen stops
Have installed screen stops on the 3 windows that can be opened and have sliding screens.
The ones I used are found in the link posted by mike837go (thanks again!)
This update is to provide some install info. The screen slide track is not very deep, something like 3/8", as received the stops were too deep, they inserted fine, but height was enough to also stop the window from sliding. Quick fix involves a vice and a hacksaw, take about 1/8" off the portion that inserts into the slide track. Perfect! This also provides a better position for the thumb screw to tighten down. No more screen movement, cats don't have enough strength to unscrew the thumbscrew, plus they don't have thumbs! But it seems like they do sometimes.