If you buy one increase the tailplane span 4" overall (cut the old 1/2" tip off, leave the elevator as it is and add a 2 1/2" fixed extension each side.
The U/C mounts are fixed to the balsa top skin, so grass use or a heavy landing can flex and crack the top skin. Lay glass cloth in the U channel between the mounts and make sure you bond all the joints properly.
With a sports wing, its then a reasonable flying aeroplane.
Dave