Hey just wanted to say thanks for the pattern. It didn't end up perfectly round and I realised it was because the pattern wasn't very symetrical. So I tweaked it with photoshop to make it symmetrical for rounder results.Below is what I ended up with, using spongy stress balls as the core.
Wouldn't have done it without the original pattern though. Thanks! Thought id share my pattern in case anyone needs it. Its sized for a stress ball, about the size of a real basball, can't remember the exact measurements though. You may have to tweak the size to fit your core.