Bronte, I received my Viperjet at the JepPower fair in september. The T nut was also on mine, makes the vertical sit very secure!
However, the trick with removing 2mm on the lip at the rudder, would not help me, I had to mount blocks of varying thickness to align the rudder correctly to the fin, otherwise the top "horizontal part" of the rudder would not "lay flat" on top of the vertial stabilizer.
But, whatever you do, make sure there is wood inside the surfaces for the horns! The last 3 we have here in Denmark had none (or only some), and glue that canopy glass securely, and don't trust the chinese glue used