Hi, Welcome to RCU!

I once had the 40 size Funtana with a Saito 72 in it. While it is not a big plane, the control surfaces are large. You don't have to over do it with servo strength, but for 3D I think you need something high torque. The Hitec 635 is a reasonably priced servo at $29.99. If you run it on 6v it provides 83 oz of torque. That is plenty for this plane. If you don't like Hitec servos you could go with pretty much any servo with at least 70 or 80 oz and be in good shape. Good luck!