I've been running this tank for two months and I've notice based on filling up and mileage that the gas light goes on with 5 gallons left(fill up tops out at 25.5 gallons from this point). Is it possible my fuel pump can't reach the bottom or is that just how it's approximating what's left with the greater quanity? I'm admittedly paranoid about running out. I typically get 17 mpg, so 510 on a tank, but obviously I'm not running dry however, the light will go on 400 miles into a tank. I have an oem replacement pump in. Maybe Im remembering wrong but previously the light would go on with hardly a gallon left. Anyone else have this tank running a stock pump or something else? I want to fully exploit the range since it cost a fortune.

Since the tank is bigger, the sending unit on the pump is probably out of kilter now, as it was designed for an OEM setup. What I would do is on your next fill up, Take a 5 gallon can with you, and fill it up as well. Then, run it 'til it's dry. Make note of the mileage when the light comes on, this will be your "reserve" starting point. When you run out of gas, make note of your mileage again. Add the gas from the can and go fill up again. Then you'll have a good idea of range, not only for a whole tank, but your "reserve" as well.

Other than that, how do you like that tank? I could see myself parting with the coin for one, but would like to know some other info on it...will it work with a OEM skid plate?

Not a bad plan, ill give it a ahot. It actually has a built in skid plate. You won't be able to relocate your rear axle if you have it in, otherwise I think it's well worth it.

it really depends on the dimensions of the tank and how it added capacity..

the range of motion on the float for the sender is only up and down so if the capacity is added to the tank width wise and not vertically. What you're saying would make perfect sense. Just the same as the half full line no longer means half of 20gal or whatever the previous capacity was.

The light on my 99 comes on at 1/8th of tank, when I fill it up then I've never put in more than 16 gallons in so 5 gallons sounds about right for a larger tank.

I had to Google it because I've never heard of it, but wow that seems like an awesome mod. Pricey, but nice. Good luck figuring out your fuel sensor issue.