First of all - if your mallets are staying on the bar long enough to "dampen the "tone" of the bar, maybe you should switch to violin or saxophone - marimba isn't for you. The Bethancourt mallets are prized by (educated)mallet virtuosos worldwide. The reason nobody can duplicate the Bethancourt mallet is because Jose took his secret to the grave - even his son doesn't know exectly how it's done.
You have to take a test to drive a car; you need a permit to have a picnic; but they let anyone become a percussionist - sad.