Pinpointer coil for Surfmaster 1.2

[andreapas79]

Hi everyone, I would like to build a coil around a ferrite core to turn my Surfmaster into a pinpointer if needed. Do you have any suggestions?
I thought 400 turns, with a ferrite bar D = 10mm L = 80mm, wire D = 0.35 enameled.
Could it works fine?