It was decided to replace the existing hammers which were not actual Steinway parts but probably some sort of asian knock-offs.  All the the balance/front rail felts had to be replaced.  Therefore, it was necessary to set the key height to the requisite 2.594″ above the keybed, etc., etc.  Plan on spending some time because everything changes with the new felt.  Genuine Steinway hammers (NY improved)  turned out to be an impact player – tall that brittle harshness was now gone.  Tonal colors could now be discerned, even prior to the shaping & voicing to come.