leak at sending unit

I seem to have a leak-free installation (for now). Trying install the sending unit when the tank is on the car is way less than optimal. I decided to remove the tank and give the installation a better chance of success. I compared the new gasket to the old and thickness was the same. I used the wood handle on a hammer to tap down the tabs a little, placed the gasket in place, set the sending unit in place over the gasket, and then put the lock ring on. I noticed that the diameter of the lock ring was almost a 1/4 inch smaller than ideal - so it would be easy to install it far enough off-center to allow a leak. I don't know if I could have centered the lock ring while the tank was on the car because there's little room between the back of the tank and the differential and visibility is poor

For now, the tank is sealed up, there is gas in the tank, and there's no sign of leakage. I'll let you know if I run into problems after the tank goes back on the car.
tx,
Ken