One of the first things I've done is to fill the balance weight stub with Black Silicone sealant.
I had to alter the metal threaded bracket that normally covers the opening to allow this. Its basically a threaded insert, a right angle bent piece of metal, with a threaded hole in each limb. One hole to take the fixing screw that retains the copper tag on the underside of the stub and the other on the end of the stub to take an additional threaded weight. I simply cut off the portion of the bracket that blocked the end of the stub and left the rest to do its job of retaining the copper tag which holds the large main weight in place.