Convert the trk file to def using N3Def program and scroll down to the banking section. the first line is usually the outside ouf the track, make the first 3 values 0, the next one the banking value you want, and the next two 0. Do this for all sections. Then open the 3do and move all the outside points w/ walls up or down to the banking value you entered. Play around with it, it's not as hard as it sounds, and yes, those banking values are gonna be kinda big.