I would like to see an actual answer to this question, as I am having the same issue. The SSO logs in and I can get the info into the Login bar, but when I try to post a question as a different user it defaults to a previous user. Along with that, all of the "points" are being prescribed to all users - regardless of who is logged in.
I have been trying to trace back which function this would be handled by in the external users file. The question says, Problem Solved - but how?