Place the
hatch about 3/4 meter forward of where you want the breeze. [This is a trick that has to do with how air flow works.] And, if it will be a clear hatch, also make a cover for it to protect the
acrylic "glass" when you want the shade.
Acrylic canvas or shade cloth will do. You will also want to reinforce the coach roof on the perimeter of the hatch, so that the hole doesn't weaken it, and the hatch, can be properly installed.
Ann