I am flying a SYNERGY 90 3D for 2 years now, and over 250 flights on it.
I have set up conditions on my Radio for both F3A kai 3D performance.
If you do not push it on 3D manouvers, and fly F3A style,then they should be fine.
If you push it, then it is better to go to stronger servos.
I started by using Futaba 9252 on Ailerons and Elevator, now I have setled on Hitec 5945's since in 3D the plane showed that it needed more torque servos.
I never use 6V on my planes only 4,8V, since I want to have the B failsafe from my Radio as an extra security measure.
Excellent flight performance, Good quality, attention to detail, you made the right moove buying it, just brace the tail !!!

Baper[8D]