I am fitting a copper foil. I fit the first shell by using first ss path and got it fitted nicely. Then keeping the parameters for the first shell to be fixed , I tried to fit the second shell by taking first and second ss but it is always coming a littel displaced and not fitting well also. But when I added the the third ms path to it , the fit becomes very nice. But the problem is that parameters for third path are coming very bad. And one more problem is that the value of SO2 for second shell is coming very high around 1.5. I am not able to understand the results.