Hm. Not sure where my reply went two days ago.

Anyway, so you'd need to find the highest z-index within the body stacking context. Which would require recursing through all the elements that are contained in an element which does not create its own stacking context.

And given the ui-front and tooltip classes use fixed z-index (9999 and 100 respectively), I'm going to guess there is no decent way to resolve the z-index dynamically.