According to this document "EUROCONTROL Specification for harmonized Rules for Operational Air Traffic (OAT) under Instrument Flight Rules (IFR) inside controlled Airspace of the ECAC Area" everybody needs to stay within 1nm and 100' of the formation leader.
F-16 are not RVSM approved, but normally during ferry flights we get to go above FL280 to be able to get to our destination without a fuel stop. Best cruise for the model I fly and when in tactical configuration is from FL320 and up once the fuel is burned.