RH 10 Style Sheet setup in Single Source Layout

I would like to apply a different style sheet to different output in multiple single source layouts. I went into Webhelp Settings>Content Categories>Content and clicked Apply to All Topics, then selected the appropriate style sheet from the CSS dropdown. I did the same in another layout with a different style sheet. It didn't work. The only way I seem to be able to attach style sheets is through the Topic List. Is there something else I need to do first to get that switch to work in the layout?

Thanks!