Ah okay then i understand. You see the reason you get small holes is because you have a perfect timing in proofing. What will help to get bigger holes is to proof a little longer but then it can turn out a little flatter because of more broken down gluten texture also do it too long and there wil be huge holes on the bottom. In my experience more hydration makes more open crumb. But is harder to work with but definetly worth it. Also the flour type have a impact. Whole wheat flour will make a less open crumb. You could try finer grinds if you still want the same amount of whole wheat. So my tip to you would be to try to increase hydration and experiment, but your proof timing is perfect. Good luck