An experiment with the size of the bowls on the 8. I think the right-hand example is the happy medium between the other examples and looks closer to a stereotypical 8.
6s and 9s are a two-in-one as a 6 is a 9 rotated and vice versa. Pretty obvious really, but this demonstrates how the two numerals interact with each other.
Here are the final numerals, that I think look consistent with each other and the existing typeface.