[Mr. Lim]

Dave,

We need to talk =).

Are you using motors that will backdrive?

How fast are you raising this thing, and how much momentum will there be, and thus how likely is it to overshoot your target?

How many positions do you need to move this thing to?

Without knowing the details, I'll put money on doing two things:

1) using the 10-turn pot (encoders + a homing limit switch are a pain)
2) finding a way to mechanically preload your elevator so that it takes roughly the same effort to raise or lower

If you can do 1 and 2, then the built-in WPILib PID classes should get you what you are looking for. You can even use last year's mecanum code for reference, although you'll need to modify the input from an encoder to a pot.