For those targeting .NET 3.5, you will notice that RibbonWindow’s Height, Width, Left, and Top properties are a little funky and can be misreported. This article explains why RibbonWindow on .NET 3.5 has these issues, how the issues manifest, and how to work around them.
The Ribbon RTM release was built against .NET 3.5, but our October 2010 release of Ribbon includes both .NET 3.5 and .NET 4.0 Ribbon DLLs. With the v4.0 Ribbon, we have enabled ClearType on all of the Ribbon controls using RenderOptions.ClearTypeHint. WPF applications using RibbonWindow must also opt-in to enable ClearType for all content below the Ribbon.