Some of the original tanks and all of the replacement tanks I've seen are actually a bit taller than 11 inches. There is a horizontal baffle piece in place (cut so that fuel will flow through) slightly above the bottom of the tank...maybe an inch or less. I haven't really cut one apart to look since around 1972. Point being when your float hits that baffle piece (which in mine was 11" from the top) you'll THINK you're empty...but you will have enough to keep going for a while. As for leaving room at the top, no...I would not do this unless I planned on having somebody leave the ignition on and use the fuel gauge to judge how much gas was in your tank (maybe you don't want to fill it up?). I'd make certain the float hit the top of the tank when it was full. That way I'd know the tank and gauge were in concert. Just my thoughts, Darren.
