I spent an exorbitant amount of time on this exact thing (IIS redirect attempts) with little success last year. What I ended up putting into place was an .aspx page in the web site directory with the following line:
Response.Redirect("/ProcessManager/")
I don't have the environment in front of me presently, but from memory, I believe that was all that was needed. The .aspx page handled the redirect, with no need for extra IIS configuration.