I just did this set. I thought the Light LEDs were too loose compared to other Kato Passenger cars I have done in the past. So on the backside of the LED's I put a couple layers of scotch tape to help tighten up the fit, it just pushed the LED's closer to the Copper strips, at the bottom of the LED you do have to cut a slice in the Tape where the LED has its split to insure the LED bottoms out. On the Windows I also had a couple where the Windows would not stay locked in place. So on the outside of the cars I put a little tape where it captured the window at the front and back. This just helps hold the Windows in place until you get the shell back on. When done remove the tape from the side of the car and the windows are now fine. On about six other different KATO Passenger car sets I never had this problem. The rear car was set up so the Light Diffuser just clicked into the top of the seats, But I did have problem closing the shell. It seemed the diffuser or LED was hitting the top of the car. and getting the rear Platform at the Back of the Car back on and locked in place took a bunch of trial and error. I spent a hour on the rear car alone. Finally got it done but was never sure what I did to get it closed properly. All the cars do have areas to click the top diffusers in place, but these spots seemed tighter than other KATO sets I have done, and about two or three of these cars finding the spot was a bit frustrating. I like the Cars and give them 5 stars, but the light kit install is 2 stars. If the Cars with preinstalled lights are still available I would suggest buy those instead.

My dome cars have 2 light sockets only problem is with 2 bulbs it’s twice as bright as the singles

You do it wrong my friend. Put plastic white stripe on the passenger sit and then use tape or super glue then put train cover on. I did 17 passenger cars and all look great my friend.