LSV Tower Mounted Mirror

Our 2007 LSV has a Moomba big mirror mounted on the tower that is right in the way of my view looking forward. I took the mirror off and now want to remove the piece that holds the mirror onto the tower off. Does anyone know what type of wrench to use? It looks like an allen wrench, but I can't find a good fit, tried all metric & other sizes. Also tried to have our local inboard shop take it off and they had no luck?

Post a pic so we can see which one you have and maybe we can help. There were several different kinds of tower mirror arms.

BTW, you can sell it in the classifieds on here as many folks love having the mirror up high.