I have the stern mounted on a rail as well as some clips on the all round light and a bow rail mounted unit. You need a 1 1/4 inch rail mount and they cost about $90!
There are photos in Tom-a-Hawk's album, page 4 of "Seattle Cruise, John's Pics", second down on the left. I don't know how to post photos on C-BRats. I tried the Img thing but cannot get it to work.
I used SS hose clamps to clamp a SS flagpole to the overhead all 'round light for a middle flag.
John