question: dualbutton css

How do you make the dualbutton always appear like the last two sets of screenshots (as it does on hover)?

I’m looking to make dualbuttons always show their dropdown button with a real button like look.  This dualbutton reply button is  going to land in Thunderbird 3 soon and I’d like the style to look correct for both Linux and Windows (Mac is using its own button style).

dualbutton-dropdown-hover

However this doesn’t appear to be some kind of toolkit CSS hover issue. The windows CSS is decidedly worse than the Linux right now so that may be a separate issue all together; and if so we can attempt that in the same way we handled the Mac.

Hints, answers, and the like are greatly appreciated in the comments.