These guns are dangerous you are going to have the same problem that black powder shotgunners have, in the event one of your barrels misfires you would not know it, and if not noticed you may make the potencial mistake of loading a barrel twice causing way to much pressure, and quite possibly blowing off your face. Just somthing to think about!!!
I have seen them before in pictures and books but have never really wanted one. They are simply an oddity to me.
Rickrem- To prevent double loading it is practice to mark your ramrod with a loaded and an empty mark.