New gas tank leaking twice !!!

I had same issues. Difficult part is it seems to take a few days for the leak to develop. What I did on my 2nd attempt was to reuse the old lock ring, put a little lithium on the gasket, and I filled up the tank (out of the car) maybe 3 gallons. Then I turned the gas tank up on the side so the sender is now at the bottom of the tank, all of the gas sitting ontop of it. And I let it sit that way for day. Then checked it for leaks. no leaks, so then I empty the gas, install into car, and filler up. Still no leaks. Now my only issue is the angle of the float is so far off, that when I hit E, I actually still have 5 gallons.