So good to see old iron saved and renovated. Good pictures on the flickr link. Is the stoker's end of the boom/gutter tube open?
As for $5 Arai... well I guess you must have been a very worthy being in a previous life. Could sell the old brake to pay for the powdercoat! Are you happy with the reactor arm anchor? It looks bang on to me.
Anyway will be nice to see pictures of the finished bike, total eventual weight, and a picture of a happy tandem couple on the appropriate thread here at BF.
WPH