I've used several designs and although the winged versions are the most spectacular they do have a lot of disadvantages. They are relatively heavy and need big wings to lift a moderate load, and if the angle of the line is to steep they won't work. The biggest advantage is that if your kite can support the load you can get it up. It involves a double flying line and a simple release mechanism. Cut a vertical slot in the front both on the top and the bottom.
Next stage is to file out a circular piece at the rear bottom end.
They are tied to the tube. This is because the line should not touch the top of the wire loop,even when it carries a load. This is the way things should look if you've attached the transporter to the line. Both lines should run through the rings, and the clip should not only connect the ends of the line but also be secured to the transporter. When the wire loop hits the pulley it will slide backwards and release the load.