I'm getting a little closer but I still don't complete control.

I found the System.Web.Services.Protocols.SoapException class.

This works well in a web method.  But when I raise one from within a custom
filter extra stuff is added.

Here is how I raise it:
throw new System.Web.Services.Protocols.SoapException
("Filter message",
new System.Xml.XmlQualifiedName("name","http://namespace"));

And here is what I get in the fault:
System.Web.Services.Protocols.SoapException: Filter message
at MyWSCustomFilter.MyWSCF.ProcessMessage(SoapEnvelope envelope) in
c:\documents and settings\abean\my documents\visual studio projects\
customfilterws\mywscustomfilter\class1.cs:line 24
at Microsoft.Web.Services2.Pipeline.ProcessInputMessage(SoapEnvelope
envelope)  
at
Microsoft.Web.Services2.WebServicesExtension.BeforeDeserializeServer(SoapServerMessage message)

How do I get rid of all the extra stuff.