Thanks for the article. I understood HSM only very vaguely before.

I'm concerned about your use of "allow updates". I was sure that this was removed from SQL 2005 and later, and this thread agrees:

http://www.sqlservercentral.com/Forums/Topic466853-149-1.aspx

Why are you trying to update a sys table [which might be a view] to edit the thumbprint? Isn't this something Microsoft supports through a sproc?