under the hood of my canadian micra it says 5 degrees ATDC i am guessing that stands for After-TDC? I have never seen before on any other car. I am going to try 0 degrees and if i don't hear any pinging, i will try 5 degrees BTDC, and if still no pinging, 10 degrees.
for your racing application, seeing as it is oval there won't be much accelerating, more just maintaining of speed and taking good lines through corners so you can probably advance the timing quite a bit before you will notice any pinging.
its usually only during acceleration that you will hear pinging from over-advanced timing, as an example, a electronically controlled distributor less car nowdays will advance ignition timing by as much as 30 degrees BTDC or even more when cruising down a freeway.