What encoding does PersistencyManager expect the Stream to be in for LoadFromStream and SaveToStream?

I have a string field in a DB table that I am supposed to load/save my diagram into as customXML.

On load, I create the MemoryStream for the String using System.Text.Encoding.Default.  I then tell PersistencyManager to LoadFromStream.  This works but seems brittle.  I would like to specify the encoding as Unicode instead of default but have had problems doing it this way.

1.      It acts as if the PersistencyManager is expecting UTF-7.  Is this true?  Does it assume Utf-7 explicitly, or does it also just use whatever the System encoding default is? (Which seems to be Utf-7 on my machine currently.)  

2.       Can I force PersistencyManager to assume Unicode?  There is a serialization filter param but the examples don’t use it and the docs are unclear.  Can I tell PM to always read/write to stream as Unicode?  If so, can you give me an example?

Thanks in advance,

Jason