Update, we are close, but not close enough...


You can see the basic structure is recognized by the game (i found the implementation of the joint and track splines by using the debug injector by JoeyWP). The lift car is recognized and placed on the track.
I also found the lift car itself needs some splines, I made them and imported. Now I need to figure out how to assign them to the car. This of course needs to be done in OVLMake, but whether they need to be in the RIC or in the RIT section, and the specific tag value to assign them to the car are secrets... Just including them in the car OVL and hope that the game recognizes them didn't work. If I try to put the track you see in the picture in testing mode, the game crashes and throws up an error complaining that the left and the right splines are missing in the ThrillLiftCar...
Experimenting, but I'm not sure I'll manage to get this working.