as I mentioned in the previous video, I added a tab & slot coupler to the front of one of the 70 tonners I purchased in an ebay auction along with the Lionel U-boat. Got both units running good, reverse units cycle as they should so they run great together and certainly will pull a lot more! Also let the Lionel U-boat join in too. Got all three units for 51 bucks and with a little TLC have three great running units.