They must have the same guy designing these things as they did for the 2000 FE400 sub tank.
The one I fitted had a sealed filler cap and needed a vent to be up above the main tank.
I had a tap between the sub and a 'T' piece to the carb.
The last 100ml in the sub would not drain unless the bike was pointing down hill. (A cunning reserve maybe?)
I remember climbing the big hill to the lookout over Bright and having to do a couple of 'U' turns to refill the float bowl.
Another memory from a great 2 day with Alan White - does anybody remember Big Al? where is he?