Nice looking setup you've got there. I hadn't realized the Supernova lights came with front AND rear cables attached (Schmidt, OTOH, only has front cable attached with sockets for the rear).
While I'd probably hook up a rack light on the rear, because it's one less set of batteries I'd have to worry about. But if I weren't going to do that, I might cut off the rear cable about 4" from the light, and perhaps install the gold connectors (with heat shrink tubing around them) for a possible future hook-up. (Where would you store the rest of the rear cable so you can find it again in a few years?)