MAS SBC mail extension is very ridiculous thing. if we allow such extension at present, In future trains might extended citing same reason, uzhavan ananthapuri has slack so extending into Ongole, nellai pothigai has slack so extending it to JTJ and possibilities endlessly go on. If u ask personally I support the move KA SF PM to MAS as MAS has more turn around time like delhi for that rake. Reliving SBC with one daily free slot to cater some trains like SBC RMM RSA SBC VLNK. MAS free slot can be easily obtained by shifting kaveri to tambaram.