I think I have went to just under 4.9 gallons, but that's not the important thing with Harleys. I have noticed that the fuel gauge moves real slow up to 1/2 a tank, then you can practically see it move on the last 1/2 tank. I guess its another Harley phenomenon.
On my '04 EG Classic, 5 gallon tank, I was very low on gas and praying for a gas station. I rode into the first station and proceeded to put 5.04 gallons in it. I would have been walking in another mile.