Hi Jerry,
Stop it, your making me hungry!
It wasn't obvious at first, but I have just realised that you have spatchcocked your chicken differently to me. I think this may have an effect on the cooking times.
I spatchcock the chicken by removing the back bone, not through the breast plate. This allows you you to flatten it out a little more as the legs and wings do not overlap or cover the breast meat. This should help to give an even cook.
I've Googled this and came across the following
http://youtu.be/l-8tMEwBnSA I picked up on the Keel Bone removal, which I don't normally do but will in future.