RE: Low tail in turn
By extending the nose you have added more lateral area ahead of the CG. What this has done is make the fin area inadequate to handle the aerodynamic balance in turns. My Seamaster 120 did exactly the same thing and it was almost impossible to steer through the corners. Mixing in a lot of rudder helped (80%) but it was still imprecise. The solution came from the addition of a pair of subfins beneath the stabilizer. Now it flies great. The total area was about 30 sq. " for the two fins.