I've made a cap with an ordinary baseball cap replacing its brim to transparent with color. I found it is useful to throw a glider to the shining sky and to trace the glider.
The cap with transparent cap gives me a wide view to the sky, and then prevents me from losing the glider out of sight. And now I don't need a sun glass to throw gliders.
And here is a Visio drawing to explain how to make that cap.
