Those servos are fine for a 30, but I went for a few servos with higher torque so that I can transfer them on to a 60 size later. I think the 9001's are about 4kg/cm . I went for 9.5 for collective, about 5.7 for cyclic and 2kg for tail. I am using a digital S9253 for the tail which comes with a GY401, but 9251's and 9252's are good tail servo's, but it depends on the gyro you use as to what tail servo you will use.

If you move onto a 50/60 size, I think 5.5kg/cm is the minimum recommended torque for cyclic but am not sure for collective. But those 9001's shall be fine on your 30, I used standard S148's for months without any problems.

James