This is my first engine that I’ve run into a problem of not being able to get the shell off. It is a 6-28241 C&NW U30-C #935. I want to address an issue with the cab lights and need to get the shell off. I removed the two front and two back screws but the shell is still on tight. The Lionel parts diagram shows two additional screws in the middle, but they are not visible. I took out the four screws holding the fuel tank/speaker enclosure but that didn’t come off. What do I need to do to get at the remaining screws holding the shell on? Thanks in advance for any helpful advice!