Well, I tried that also but it is not working with MetroUI skin (see attachment). Some other skins seem to work differently. That border does not look good with status bar… TsStatusBar is slightly better thou but still that border feels too wide. I choose another skin, no problem.
I think it is not a good idea to have that border width as a skin option. It is ok, when you only use one skin in your application. But if you let users to choose the skin then your application borders look different and it is quite a painful to fix those borders skin by skin in code.