Per the event supervisor:
Question: Can you change the overall height of the device while leveling it as allowed by rule 4.c "Participants may level their Roller Coaster at the beginning of their time to account for an uneven floor or table."?
Answer: No, rule 3.g "...Parts and track can be added or removed, but the overall dimensions of the device may not change during the competition." These rules are not contradictory, it is possible to make a device that can be leveled and does not change overall dimension.
Question: Can I use wedges to level the device?
Answer: Yes, but the wedges (or any other leveling method) are part of the device and must meet all other rules, particularly para 3.b on overall size and para 3.g "...overall dimenions of the device may not change..."