amortized presser foot magnetically

to damp the vibrations of my printer I designed and made ​​of ABS a presser foot up two neodymium magnets in opposition.
Most are big magnets greater is the force that opposes the weight of the structure.
my printer that exceeds 30Kg I used two cylindrical magnets from 18x5 mm, but are just enough
http://www.youtube.com/watch?v=Rr9P2ksy52Q