When to shift?

When you build something special it makes sense not to waste time runs on tuning, all my competitors seem to have the car set before they show at the track, and I get beat to the 60', but i still get them off the line, and I dial according to the time runs. Tuning at home for the next time. The videos of the car give me the evidence for changes.
As long as your having fun do what pleases.