I think wide radius track makes the difference. I am also convinced that the shape of the T-rail-head gives me more traction. I have a 2025 for the lead engine, because it was my best smoker and is the same as a 675. My coupler pilot is on a 675. I had a successful run with 6 cars, then spent some time cleaning and oiling wheels until I had 20 #6454 type 8-1/4" boxcars and 2 lighted cabooses, total 22 cars, 24 if you count the tenders. The tenders that I used have the whistle wiring removed, so it would not give any trouble. Using a prewar Z 250W transformer, I ran the train on my outside main line. I synced the E-units in forward. The train had no trouble at start-up, no slipping, and both motors have Baldwin Disc drivers with slick SS tires. It ran smooth at just under 15 volts (on the dial). With no slippage, I am not at the limit of the 2 locos. 072 T-rail and all cleaned / oiled wheels makes this possible. I was surprised and pleased with the results. This train is ready to star in a "Double header / Unit Train" video. I also noticed that I got a lot more smoke output when the locos were working harder pulling 22 cars, than with just pulling 6 cars. I will post some photos.