Bad idea. You're changing the magnetic flux of the magnet to a different parameter than before, using the same coil. You won't end up with the same result.
The 70% BL method of excursion will likely be lopsided as well as cms. This is not a good idea unless you have the proper software to model the magnetic field and properly align the coil in it, and have a magnetizing machine and know exactly how much voltage will give you what kind of magnetic strength with ceramics, and specific to that mass to get a desired BL.