Also, if you ever want to remove the Arai drum from your hub, you can make a cheap removal tool with a 2x3 or 2x4 piece of wood and a couple of long bolts + a few washers and nuts. Measure the space between two of the Arai removal holes on the drum, drill holes in the piece of wood to the same width, and then thread the bolts into the holes.

Or, you could buy the spiffy tool from TandemsEast (and maybe other tandem vendors) if you don't want the hassle of making one yourself.