OH! I should mention that I can't do this:
Then head into the slideshow's settings and hit 'yes' on "Shrink slideshow's height when width shrinks" (The default is 'no').
why? because the height does have to be set to 480px for the Desktop version. but I want it to be auto for mobile.. hmmmm unless I can set it to 480px via CSS for desktop! I'll try that way too!
thanks so much for your time!