I'll be very happy to give you detailed instructions on my porting process. The base is DragonFF which made this possible. The first step will be to make it support Vice City, which won't be that difficult - I'll be able to do that, I wrote the map importer so I'm familiar with what to do and where. Then it's about importing every section of the map, and doing very specific procedures to it in Blender. I haven't had any issues with the collisions. I'm just using the visual model minus foliage and decals (dirt, shadows, road markings..). If you really want, I can make a video tutorial to make it clear what you should do in Blender. It's not hard, but time consuming, which is why I probably won't port any other map. Liberty City took me ~2 months (working only on weekends). Also, the more map segments you make, the better the map will run, but the more time it'll consume. I settled on 36 static models each with it's own LODs.