Hmmm, that's interesting to know!!! Of course I am not the pro at this like you are - I was just siting the book.
However, I have not had any difficulty with the HH as I did with the Bentonite. But then again, I have yet to pass any "rubbery stuff". I am however, passing some very dark stuff - which again, the book said would happen instead of the "tire rubber". I will keep you posted on my progress.