I've gone my own way with installing the V tail, and cut little triangular pieces to fill in the void between the flat seat for the tail and the V of the tail, hopefully the photos will illustrate it okay. As far as the instructions go, they seem to suggest just CAing it in, but there is such minimal wood to wood contact area it just seems wrong.
The more work I do on this the more I'd like to get another one just to try and get it right next time, it's not gone together totally satisfactorily, but hopefully it will fly well on the slopes.