Chic,
felker 14 provided an answer in the above post. Note you can also obtain the Festo Reducers 6mm-4mm, P/N FES SM6-4 or the Mini Air Trap , P/N MAP-MUAT, directly from DreamWorks along with their Hanson Super Trap. I would simply go with the Festo 6mm-4mm Connector.
What is the size or the manual fuel shutoff valve for your Super Bee? Festo make both 4mm and 6 mm Ball valves which are also available from DreamWorks.