Custom Extension Accessing properties from the project amp file

[JosephCox]

I found an example of how to access properties from the amp file at arcgis mobile 10:
http://forums.arcgis.com/threads/35760-Custom-Tasks-and-Accessing-Settings-from-AMP-file

but the readXML and WriteXML methods in the esri.arcgis.mobile.client.ProjectExtension are obsolete in the new version. Has anyone successfully read or written to the project amp file using the new ReadJSON and WriteJSON methods?