Every time you create/convert a track it's a good idea to check it's track length and compare it with the real counterpart.
You can do it in a very easy way using telemetry.
The steps to follow are few and extremely easy:
1) do few laps in your circuit (at least one complete lap after the installation lap)
2) in the race studio analysis (the AIM telemetry software) select from the menu file>Import netkar file and select your {my documents}\netkar pro\aim\telemetry_dump.nkt
3) double click on the new telemetry data just imported


4) select Channel Report from the menu (or press ctrl+F4)

5) compare the measure you got from your test with the real track length and resize your track, eventually.

You can download the AIM Race Studio2 telemetry software for free from the producer website

Nice Tutorial