I always carry out an ECM fitting using Zview Software. In this software I model each semicercle and find aprox. values, after that I fit with this values all the ECM. In your case, I'll find in the first semicercle the values of R0, R3A and Q3A, then in the second semicercle R2A, Q2A (knowing R3A) and finally the last values. With this values fit all ECM.