I have it...and I intend to use it, as you can see straight through the hull in some spots, especially aft of the conning tower.
My logic is thus...if you bought the kit, all the PE, and the wooden deck, what's another $40? I spent double that watching my local high school team play the Pats on Sunday...oh wait, those were my Colts!!
I would also recommend Steve Nuttall's turned brass scopes and gun barrels, and prop shafts as well...beautiful stuff!
Jeff