Thanks for the quick response, the labels are fine now but the plus/minus buttons are not yet fixed.
I was surprised you use WinForms btw, because of the the skinning I always thought it's WPF. I've also done a larger WinForms app (StaxRip dating back to .NET 1.0) with lot's of custom drawing, WinAPI calls and so on, next app I definitively try something different like xaml or html.