Do you want this to be a permanent type of fixture?? I recently bought some tower clamps from http://www.proflighttowers.com/
that I was originally going to use to make my bimini...I ordered four, but only needed two, so what I did was order some 1" bimini hardware(1 end cap and 1 Jaw slide), and got a piece of 3/4" conduit, placed the fittings on the conduit and screwed the bent conduit to my tower clamps...it's easy to remove, and most important (to me at least) not permanent. The clamps ran about $45 a piece, so you may not want to spend that kind of cash for a flag mount, but I think it looks good... I will post pics later.