Awesome I am seeing that if the creature adjusts sizing via the "size category" adjustment the damage does scale pretty much as I was intending.
@Mathias
One issue I did come across that's related, is in the "Race Builder", in the portfolio itself when you change size there, the natural attacks damage die don't scale, only the extra damage due to the size change.
For instance:
Code:
Medium Creature with Slam (10 in all attributes) = +0 1d6
Adjust to large in the drop-down = +0 1d6+1
Adjust to small in the drop-down = +1 1d6