I have about 40 Athearn Spline cars with trailers mounted on them. As suggested, I added about 1 1/2 ounces of weight to the floor of each trailer. The train turned out to be fairly heavy. The problem I am having is that these cars are still top heavy and occasionly they will tip over even on large raduis curves. I would like to add more weight to the cars to lower the center of gravity but am at a loss as to where to put it. There just is not any place to add weights that would not distract from the appearance of the car. If anyone has any suggestions I would certainly appreciate it. Thank you.