The Brodak P-40 ARF has built up and balsa-covered tail pieces. They are very heavy. Pat Johnson (the designer) recommended replacing the tail with lighter pieces. Also, his own P-40 has a bit of wing dihedral, which he recommends for better flying. These changes wouldn't be very difficult if you started with the ARC, or stripped the film from the ARF, and refinish in silkspan and Brodak paints, like I did.
Floyd