It occurs already with segui light 9pt., so there's probably something going on.
Ok, hold your horses, I think I know what is happening.
I have the bottom of the info panel relative to the bottom to the main panel, and the top of that same panel relative to the top of the main panel. I believe the values I have set there stretches the info panel to begin with.
I'll see if I can get it to work with both being relative to the bottom.
Or maybe better, I'll see if it works when I completely remove "<top relativeTo="Panel.Top"
To my understanding that entry serves no purpose here, just the starting point from the bottom should be enough.