[Ifeffit] Shells in XANES

Hi, I want to estimate the influence of every shell in XANES simulations like Bruce Ravel shown in the publication: "A practical introduction to multiple scattering theory" I always done simulations until the system is converged, so now I have a doubt, should I increse the SCF until convergence and add new shells in FMS to repeat this kind of results? Thanks in advance, euG