A smaller tail wheel? more expo on rudder? sounds strange.....if you were the one with it shooting straight up that sounds a bit counter-productive in fixing the problem...i have a big sullivan tail wheel on mine, which is for airplanes up to 35 pounds, i have a ys110fz in it with a 16 x 6 prop tank is on the center of gravity and battery is behind the wing tube. and my rudder servo is in the tail. all of my rates are very high with expo at 45-60%. it flies awesome, snaps a little but not too bad, it flies knife edge almost no coupling ( lateral balance is good aswell as the one it says in the book ) it flies upside down almost hands off which indicates good balance, servos are 5625mg's except a 5945 on rudder, i use airwild aluminum arms 1 and a half inch ( half arm ) or 3 inches ( full arm ) i think to try to get most throw and they are threaded for the included ball links from the factory which reduces slop compared to having just a hole in the servo arm.


edit: forgot to mention why i said more expo on rudder is strange.....i find ( and this may be just me other people might not think the same ) that rudder is best with only like 10% expo because then you don't have to move your rudder so far to knife edge and the difference between a perfect knife edge and starting to angle upward ( if you can understand that ) is more of a marginal difference on the stick and makes it harder to maintain a good knife edge.