I'm not an expert, but from my experience with editing the tracks for private I may suggest you to do the following:
Extract the wad of the needed track, open the .GP4 file of the track with GP4Builder, open the scene containing the runoffs you want to edit, then search for the runoff piece itself (usually named NLAND_xx), open it and select the needed type of surface.
Illustrative picAnd don't forget to create a new .col file after the edit.___________________________________________________________________________
For a list of EVERY download for GP4, look here:[docs.google.com]Edited 3 time(s). Last edit at 09/06/2017 09:06PM by Soutsen.