First, what is the difference between RadiusX and RadiusY?
Second, I have buttons in a SkinnableContainer that are end to end, with no gap, intentionally. What I have been trying to do is have an concave border on the left side of the button and a convex border on the right side of the button, but I can't seem to figure out how to do this.
RadiusX and RadiusY gives you the possibilty of elliptical corners. so x=y is round if not you have either more vertical or more horizontal curve.
To define fit together buttons use group as the main container and disable mouse over transparent areas. for the button frame use an svg data path.
http://flashhub.net/ezflex/slider/ with source, not exactly what you want but very close