I am a relative of Gate Mudaliyar Ponnambalam of Urumpirai and have his family tree going back several generations, with several thousand other relatives. My sources are fairly similar to Soren's at a guess - the main one is the Descendants of Manipay by Thambimuttu, but I also have several other sources.
I am happy to share this with you. Please reply to my email address with your preferred means of communication - email or postal address and I will send you the material.
In return, any information you have that can add to my information would be gratefully received.