Really sorry - he is not. The whole concept of linking Srirangam with rama itself is a later concept. Srirangam is probably one of the oldest temples of tamilnadu but it did not have rama legend. No alwar sings about srirangam - rama connection. Nobody mentions about the vimana.
The sriranga vimana becomes important at later stage after jatavarman sundara's pon vimanam. A myth had to be attached. Hence the legend about sriranga vimanam - vibeeshana etc in which pillaiyar plays a role.
The lalithanguram (mahendra cave temple) in trichy rockfort is very ancient but not uchi pillaiyar. But unfortunately the gangadhara of lalithanguram hardly has any visitors while the very nearby pillaiyar enjoys heavy patronage:-)
I am from Trichy and I used to feel thrilled to hear the story behind ucchi pillaiyar/srirangam... I was even pointed to the outlines of the "sambadam" around Ranganathar (which was the box in which Vibheeshana carried the ranganathar given by Rama)
Until I heard from a Mangalorean friend about the story behind Gokarna Mahabhaleshwarar. According to her, they believe Siva gave Ravana a special lingam, Ravana was taking to Lanka and gave it to a small boy (Ganesha) for sake keeping while doing his evening prayers. Small boy placed it in Gokarna where the lingam got stuck.
It seems to be too much of a coincidence to me ;-)) One of these stories obviously is heavily drawn from the other.. a la Kodambakkam style.. which though?!