How do you set rich text in a content control

[Testor]

Forgive me I'm lost and bewildered!
I have a document with several Plain Text Content Controls. So far, I can enumerate the SdtElements in the document , find all the SdtBlocks of interest and replace the text as needed ok.
Next though, I have one field in RichText format that I can retrieve from a database as a string and now need to insert this into the document. I've set up a Rich Text Content Control in the document but how do I set/replace this with the rich text string and retain the proper formatting?
Just to make me more confused, when I open the document with the "Word 2007 Content Control Toolkit" it shows all the Content Controls as expected and properly identifies the one as Rich Text type. When, however, I open the document using the "Open XML SDK 2.0 Productivity Tool" it shows the rich text control as a plain simple SdtBlock that appears completely indistinguishable from the plain text content controls and the reflected code seems identical?
How then to set the RichText string in the document?