I believe that CalloutBox should expose the value of 'borderSpace'. I'm doing some animation and positioning of CalloutBoxes and if I don't take this value into account when I compute the size of my content component in relation to the FitInArea, the drawing of the arrow often results distorted or absent. Of course I know by looking at the code that this is
borderSpace = jmax (20, (int) arrowSize);
but that might change in the future.
Thanks for your attention!