Hi,
I have completed my bowling ball, as far as I remember, the holes have a special shape, it is not just a basic cylinder, the base (inside the ball) is narrower than the top (on the surface of the ball). So I just used one more scaling and an inset to set things right.
Here is what I created:
I also painted the ball the same color the model I used is and chose a different color for the holes, they are somewhat grey-ish.
Ready to throw that ball !
Cheers !