First off - I would not be the one to laugh at a 15 for the first time at the track - I have been there! Second - 1.9 60' times on stock rubber is great! I would say you are shifting both too soon (like 5500 RPMs... because of your trap speed) and also shifting slow (because of your ETA). It just takes practice. After a few runs myself, I have found 3000 RPMs with a controlled clutch release is the best to launch my car at - keeps the bog out and lowers your eta. This takes a lot of practice and is hard on your clutch, but you got to beat up your car to get the best times.