Hi,
Trouble lines in a dogs's form will show up in each dogs individual Standard Deviation, the cleaner the racer the tighter the Stdev.
You need to remove subjectivity out of your selections process and this is just one example.

Regarding racing weights, if you look at each dogs racing weight it will start of lighter then as it grows an builds up strength it will become heavy, then it will reach a plateau in weight with lil variation excepting for injury, then as it starts to get to the end of its racing life it will gradually gain weight until it makes its exit.
So if in general you split each dogs racing career into two halves of heavy an light weights, and look at the avg racing time of each half, it doesnt take a genius to know which half is quicker.