The tail box was inspired by pictures of Lee Wakefield's tailbox.I used a similar construction method of building a frame out of aluminum. There are two pieces of aluminum L that run parallel to the trike with some cross pieces. The picture is taken from behind the trike
From the side you can see the two vertical pieces that support a cross bar that is higher than the wheel and can therefore go all the way from one side of the tail box to the other
Here you can see a piece of recycled coroplast sign that will serve a bulkhead across the tailbox.
In this picture you see the frame with the coroplast floor of the tailbox in place
Here you can see how joints in the coroplast are reinforced with pieces of coroplast that has been scored with a knife so that it can be bent. These pieces are then hot glued into place