The last evidence that Rajendra I - co ruled with RRC - is from Tiruvalanchuzhi Kshetra balar temple - found by us during excavation and read and recorded by Dr. KKvn / Dr. Nalini - reported in varalaaru.com , varalaaru issue and book Valanchuzhi vaanar.
This off-set Kudanthai Sethuraman's postulate that Rajendra performed thila-parvatham for first death ceremony of RRC in 1015... which should have been the last rites by Rajendra to his father.
4th year - Rajendra - to my knowledge 2 inscriptions : one giving vibbodhi madal to Periaperumal ( RRC bronze) at Thanjai .. and another lavish Grant by RjC at Thiruvaiyaru ..
Let me talk to Dr. RN again and report.
This is a valid query need to be gone into in depth.
spoke to Dr. RN .. first year of RRC ends at 986. 985 + 1 = 986 30th Year of RRC should end at 985 + 30 = 1015 AD.
Also there is a published reference of 32nd RRC inscription - ASI - in SII - vol (XXIV ) ( i remember) Srirangam inscriptions - scribed over a pillar stone - which was found about 80 years back - but not any more !!
Allowing overlap 1016 AD .. was putforth says Dr. RN..
( Dr. Kalaikovan & Dr. Nalini - helped reading the inscription unearthed during Ksetrabalar small temple excavations in tiruvalanchuzhi - that RjC's 3rd Year of co-ruling was RRC's 29th year !! )