I have a Bachmann 2-6-0 Alco a fine running engine. I also realize it's a small and light steam loco. I have 1% and 2% grades everywhere on my layout. I can pull 4 cars (40 ft. boxcars all smooth and free rollers) with this loco, any more than 4 and on a grade the engine doesn't move, just spins. I'm not trying to be unrealistic that it could pull 15 cars but would like to pull 6 or 7 cars with this engine. It doesn't appear there's much room to add weight to the engine. Is there any kind of traction that can be added to the wheels that work, or would it just gum up the wheels with little or no improvement? Haven't added weight to the tender, think that would help? Just trying to pull a couple more cars. Open to ideas. Thanks, Bo.