George,  I would suggest that the necessary language be added to the Special  Conditions block of the Transaction Confirmation.
I would suggest the  following language be inserted in each applicable Transaction Confirmation.
"Notwithstanding anything to the contrary otherwise contained in the  sentences previously added to the end of Section 13.5, the parties agree that  the price to be applicable with regard to any volumes outside of the +/-10%  tolerance shall be the Gas Daily "Daily Mid-point" price for the day  following the day that the parties discover the existence of volumes outside  of the +/-10% tolerance."

Spinnaker language