I have been thinking about this from a slightly different angle.
IMO the digital fuel guage on the 2004 - 06 bikes is not accurate, as in the bars don't really correlate to true tank capacity.
So I have recently started looking at how many miles I get from full until my first bar is gone.
My best so far is 46.1 miles. I have run out of petrol on my last bar at 32 miles. I find that once the first bar has gone then the remainders disappear with alarming speed.
I fill up on the center stand, as many of you have said and fill my bike to about 1" from the filler top. To do this can take five minutes as the fuel settles. I have managed to get nearly four litres of fuel in from when the filler appears to be full.
Nelly