I made what I call a Setup File out of the original Performance File, all the teams looked like this, I then changed My Driver's numbers, I would then do a Non-Championship Qualifying session to see where I was on the grid.
If I was too slow I went higher, too high went lower until I found myself somewhere in the top 5, I then copied the numbers of My Driver on to the original Performance File.
keep in mind that all Tracks run different, so if you're like me and you want perfection or close to it, you'll have to do the same to each individual track. Unless you're running the Generic Performance File only.
[Team #07]
Name=Toyota,Toyota
Performance=800,800,0
First Driver=16,cristiano da matta,15676,0,15676,0
Second Driver=17,olivier panis,15303,0,15303,0
[Team #08]
Name=Jordan,ford
Performance=800,800,0
First Driver=18,nick heidfeld,15904,0,15504,0
Second Driver=19,My Driver,16733,0,16733,0