I thought about an idea that i think would be very nice.
maybe you can support syntax inside the tooltext , something like this:
this one should be set under the "Chart" tag property and not on each "set" property.
and than it would be easy to change the default tooltip.
cause sometimes the tooltip wider than the flash movie.
and than we have a hidden tooltip.
so... just a suggestion.
hope you'll find it usefull.
Thanks,
Shachar.