I have built up Pitch Car with all Expansions at work (there is a room which isn't needed right now). We play every Friday and came up with a house rule for this expansion:
If you fall down from the upper level and you land on a track this is a correct move, but only if it is to the player disadvantage. It is no correct move if there is one point in time when the whole car is not on some piece of track (or, while jumping, not above a track).
Here is our current track:
If a car going up the ramp and falls down (ie at the position where the green car is in this image) it has to stay there. Actually this happens quite a lot.
We have a lot of fun with this rule! Oh I nearly forgot, it is also allowed to throw someone down. This gives some interesting situations at the crossing. There were situations when one player tried to hit another car, missed, and then jumped down.