when I did a SSO for Exchange within DNN, we modified the exchange files, and removed the signout links. I'm not sure if the peoplesoft app is structured in such as way you could this, but that's what i've done.

another option would be to have the server signin and request the page, then you'd render the stream to the response while using some RegEx to match the signout link for removal. You could also remove the frame completely and just render the html directly to a placeholder with this method