hmm you are right.
i filled it up sitting on the bike, also filling way past up the neck and got up to where the seals for the filler cap go. then it went down, then i put more in, then it went down. i got about 2L more in it.
got my 6th bar for about 40k's.
that's 40k's more than my 280km so i guess i will make it past 300 after all. will post how far i go and what mpg when this tank is done