[Ifeffit] delR and sigma2 models for multiple Scattering Paths

Hello to all. I'm currently trying to Artemis fit a molecule that is highly symmetric with multiple scattering paths playing a large role. delR and sigma2 have been handled rather well for all of the single paths. I am, however, confused as to how to handle it for multiple scattering paths. Reff for them seems to be close to the value of the furthest atom, but is always ~5-10% off. (which would be my second question, how is Reff determined for multiple scattering paths) I've looked at the presentation and examples, such as FeS2. I am trying to incorporate all of the same variables used in single scattering paths for multiple scattering paths the best i can. Thank you ahead of time. Mikhail Solovyev