Read original post by Tony Champion at .NET Rocker
One of the added API features of the new Silverlight 5 PivotViewer is the ability to define a custom detail pane. It is rather simple to replace the style with your own, however, then you are left with the task of implementing several features that you most likely want to keep (like when to show and hide your detail pane). There are also a few other states and navigation features that would also be nice to keep.