Hi Simon, I had great fun with the closed loop system
, but life became so much more enjoyable when I put the servo in the tail, so in my humble opinion if you can get the CofG with the servo in the tail go with that.
I also used a Sulivan tail wheel where the steering is done via a spring attached to the rudder, I think this helps soften any shocks that are transmitted from our rough ground to the servo.
I should say that mine is the MythoS, but I think they are so closely related as to not make much difference.