What would be a good plan for a controlled Vicodin withdrawal? I am
currently taking 50mg/day for a bad back.

I strongly suggest that you don't attempt to plan your withdrawal
based upon the advice of strangers from the Internet. Your physician,
who is aware of your medical history, is the best person to consult.

During a long hospitalization, I became addicted to Percodan in the
early 1980s, and without the assistance of my physicians, I might not
have come through the withdrawal period. I wish you the best.