Length is an exact measurement, PID is a control loop algorithm that dampens overshoot and undershoot of a response to process change, not a way to attain an exact measurement. The two concepts are not exactly mutually exclusive, but what you are asking about is like trying to get your car to stop in the next town by setting the cruise control. They don't have anything to do with each other.
It sounds as if someone was trying to do a cut-to-length process by timing only, which is inherently inaccurate, now you are trying to cure the inaccuracies by trying to slow down the feed rate as it approaches the target length, thinking that the error is overshoot. That may not help, because if you are not actually measuring the length you are not removing the error, just your perceived CAUSE of the error, and that is not likely the only one. But if you ARE measuring the length and there is overshoot because of inertia, then that might be helpful. If you can describe the problem better we may be able to help, but otherwise we are just guessing.