The main recommendations for the Rail King Aerotrain is to add weight to the engine. I just got an Aerotrain and made a box to hold and attach the weights to the Aerotrain engine. Requires adding 1 hole to the frame. I have uploaded it for the 3D catalog with details.
The box with weights. Not designed for specific weights, but I got 13oz of steel, 1oz tire weights in it. Still some room.
Attached under the engine.