i have umbrella mounts at several locations in my boat, and carry the umbrellas in storage. they work great for knocking the hot sun off of you. im enclosing a photo of the umbrella mounted, and the way i have the mount hooked to the boat. this is adjustable for any angle you want and you can block the sun no matter how high or how low it is. a half inch bolt is mounted in a piece of 3/4 in conduit, then a piece of half inch conduit is slid in the bigger conduit, cut to the height you want the umbrella. the umbrellas big rubber handle is removed so the shaft will slide into the conduit. use a small cord to tie the umbrella to the conduit to keep the wind from taking it away from you.
listen with your eyes---its the only way to beleive what you hear...