@pghaworth:
The options shown in KUAL are dynamic: you won't see buttons for stuff that is currently enabled, which might be confusing for mutually exclusive stuff like the stretch/keep ar stuff.
What you don't see is what's currently enabled
.
Additionally, processed cover are cached, which explains why enabling stretch and looking at an already processed cover won't change a thing. There's a 'Clear Cover Cache' button in the 'ScreenSavers Tools' submenu just for that
. Not that right after that you'll have to switch to a book different than the last one opened for the cover to be reprocessed.