It would be good if the train leaves SBC at 19:30 PM and arrive Salem at 23:15 PM , ED at 00:15 , TUP - 00:50 and CBE at 01:50 AM and PGT at 03:00 AM and TCR - 04:15 AM , ERS at 05:40 AM , KTYM at 06:40 AM, QLN - 08:45 AM and TVC at 10:25 AM and CAPE at 13:00 PM (run little before trivandrum mail)

Return should leave at 12:50 PM and arrive TVC at 15:05 PM to leave at 15:15 PM , KTYM at 18:15 PM...
more...

, ERN at 19:45 PM, TCR at 21:15 PM , PGT at 22:50 PM and CBE at 23:55 PM , SA at 03:00 AM , and SBC at 06:55 AM (run little after chennai mail)

With PM at SBC SWR or CAPE SR train (with 3 rakes to use) , even if they continue to have RSA with 12633 then it would give sufficient time for 12634 to leave right time from CAPE towards MS with PM at SBC.