how do i get my servo to hold neutral positionwith full force

[Jakyat]

HELP!!! I am building an oilfield winch truck. I have designed a winch that runs off of 2 high torque continuous rotation servos. I am very satisfied with the pulling power of the winch, however, when I let off on the control, the servos will not hold the load. Maybe there is nothing I can do about this problem.
The servos are Hi-tec digital programmable, and I am running the unit with the spectrum 18 ch radio. I know there are lots of allowable adjustments that can be made through the radio, but I don't know where to start. I also have a hi-tec servo programmer, but I don't think that I can make this adjustment through the programmer.
Can anyone help me out with this?