To create 2-stage payload logic for Longway, I basically took ABS's multi-stage payload prefab and made the following changes:
- Deleted the third t_c_p_round and team_trainwatcher
- Deleted all the path_tracks and control points in the third stage
- Removed "mspl_round_3" from "blue spawn for round: " on the spawn point that would have been blu's last spawn (in three-stage payload)
- Removed the spawn point that would have been red's last spawn
- Removed the two "underground" path_tracks on stage 2 (the ones that the cart sinks towards after the stage is over)
- Removed the "Next Stop Target" from the last path_track in stage 2
- Removed the "SetSpeedDirAccel" on the last path_track in stage 2 (so the cart doesn't go underground)
- For the finale: Moved the OnTrigger outputs from the trigger_once, as well as the OnPass outputs that break the phys constraint and kill the train on the last path_track of stage 3, to OnPass outputs for the last path_track of stage 2. This makes the cart's explosion triggered by capping the last point, rather than dropping it into the pit. This was more of a personal decision, and if you want to keep the finale you could instead (I think) take the OnPass outputs that break the constraint, play the carttip sound, and kill the train, and move those outputs from the last path_track of stage 3 to the last path_track of stage 2 and reposition the trigger_once to catch the cart (and move the sound/visual effects to the new location).
You can skip that whole last bit if you don't want to make the finale yet. I can't recall making any other major changes. This setup seems to work, and at the least it might be a good starting point for you.