One servo per aileron is plenty - -did a few of the H9 33% models converted to one servo
The problem is when using one servo and huge arms -which can kill torque and resolution - IF the max servo rotation is not employed for regular deflection flying.
However - for sheer simplicity, use two, 811 JR on each aileron and reduce total aileron travel a bit .
You won't notice any real change in roll ,yet the plane will still be crisp and responsive.
I just finished -and have been flying a H9 330 with two 8411's in each aileron. Also just finished a H9 33% Cap and used 811 servos
Can I tell the diffeence? sure but for all practical effect, the 811's are fine.
If the ailerons are flimsy - use two small DIGITAL servos .
Th DP model is quite a bit smaller .
Even the original H9 plane was fine with one servo -provided the servo and linkage were good and the throw was not maxed out.
Many fliers have not grasped this relationship --so H9 went to two servos to minimize further problems.