This is a side view of my new truck design. I like the way it has three cylinders hanging down between the wheels. This reminds me of the springs that I have seen on the trucks of a typical American train.

Just another view. Also you can see the coupler I use. The magnets on my train kept separating at speed settings greater than four. So, I came up with this design to solve the problem.

The coupler isn't bad. It is relatively easy to couple and uncouple the trucks because there is no "catch". The black Technic plate simply slides over the black Technic axle. Also, there is no end issue. The couplers are the same on both ends of the car.