Well, that doesn't get rid of the "problem", does it? When I scale the UIPanel-Object down, let's say to 0.1/0.1/0.1 the Text-Object gets smaller, too, but there will be some labels which have different Widths/Heights because of the size of the signs/speach bubbles/etc.
I can't set the UIPanel-Object in a uniform way to handle all Labels in the Level and I don't want to create for each Label an own UIPanel :/