gas cap alignment on 65 barracuda

When I first started making my caps I only had the one slot (no adjustment ). Shortly after selling a few I started having people tell me they were not lining up parallel to the ground. After that I just added the three other positions to help solve that problem , but never could figure out why they were different. I think it just comes down to the ramp angle that was formed on the inside of the metal spout and when the cap comes tight. You could always just polish mine and it would look nice also. Thanks, Steve

btw, that cap above is for the later model car.