Glenn,
I have a piece of nylon fabric that is big enough to reach both sides. It has some holes with toggles for shock cords to attach. I stretch it from the stanchions over the boom.
Works ok as long as the wind isn't blowing hard. It's pretty low budget. If you find something more professional, please share.
Thanks for chartering your boat for the NOODS. It was good to have Jimmy, Bobby and Marty at the regatta.