I have a Superscoutmaster with rim drive. The only thing I could guess why the elimination of this slug sounds better is that it reduces resonance. You can unscrew this piece though the very back end of the arm using the appropriate Allen wrench. The 10.5i is very easy to adjust for VTA. Yes - without the slug, proper vtf is much harder to accomplish, but I found the inconvenience worthwhile to do.
VPI 10.5i mod....very worthwhile
I heard about this mod, and was slow to do it. I urge all those with the 10.5i to remove the metal slug in the end stub of the arm. Yes, I know it makes the arm easier to balance, but get it out of there and reset the arm. I found better tracking, cleaner, clearer sound, much greater depth and width. This is a very worthwhile endeavor, even though it means readjusting the arm. Let me know what you think.