I didn't do a ton of runs when it was totally stock, but i think the best was 12.43 in the winter when the da was like negative 1000.
Launching from idle will lose you a few tenths, but i think it's honestly the best way to compare times when you are adding mods one at a time and you want to see what the gains are.
As for best launch rpm when you are going for best time possible, pick an rpm to start at, if you get spin, try 100 rpm lower next time. If it doesn't spin, try 100 rpm higher. I try to always use the same road and same launch spot to keep that consistent. Different surfaces will give you slightly different results.