I was using a Snap-On 1/2" Breaker Bar and a SK impact socket. I went to Sears and got another impact socket which had thicker walls. It worked. However, the heads on 3 of the bolts were beginning to round using the SK impact socket.

I like to relieve the pressure in 3 passes to relieve stress on the head. I don't remove the entire bolt in one pass. Yes, those bolts that are not relieved will have more stress, but that is less stress than removing the bolt completely in one pass. It minimizes warpage on the head.