Before I dive headfirst into the CSS, has anyone edited the CSS from CSS Menu Designer so that the root menu titles are set to auto width, but the sub items get a set width?

I think that happens anyway if you uncheck where it says 'Use fixed widths for menu items' under the Options tab.

When you uncheck 'Use fixed widths' the sub items' widths match the width of the main list. So, if one of the main items has a short text, like "Careers", then the sub items below that are forced into a skinny box and wrap.
I want the top menu items to have auto widths (for compactness), but the sub items to have a wider set width, so there's no wrapping in the dropdowns.

No, they don't, see attachment.

Thanks.
I had to re-start from scratch. Edits I made in the CSS to get rid of borders and background colors must have thrown it off.
There's now minor wrapping, but it isn't ugly anymore.