Thanks for trying mdas, but I was really just looking for something like this:
To get the scroller in the second tier of the menu (what the tab opens), I just put my article that opens there inside of a div that had a fixed size, with overflow set to auto.
It won’t look right outside of the tabs, which would have been preferable, but it works. If there’s a better way yet to do this where the tabs impart the size and overflow attribute, rather than the article itself, please let me know. This should definitely be in the next version of JA_Tabs if it’s not.
Like this:
#menusubcat { width: 240px; height: 200px; overflow: auto; }