I had the tank out and flipped it upside down to check for how the float arm adjustment was. I had to bend the arm a bit to get mine right at full and empty. My gauge still shows full and slowly drops, but after I get down below 1/2 tank, it drops significantly faster. Not sure if its more than just the way the sender is wired versus when the tank was upside down the float was higher up than the fuel capacity of the tank lifts it.
The original sender was wired up using resistance wire on what looks like a piece of stiff cardboard and the arm has a sweep that rides on that resistance wire to send the reading to the meter. In the original sender that wire was wound in a non-linear fashion to account for the effect you see of the needle behaving non-linearly. Aftermarket senders tend to skip right over that so they can use one setup for any number of senders, they wired that board linearly and you see nonlinear behavior on the meter. After all the only thing that matters is the full and empty resistance reading, right?
