I would assume the actual items would have to stay the same as well, but if anybody needed:
Pilsen Light DME, Oat Malt, Maris Otter, Golden Promise, Pale Wheat, Distiller's Malt, Rye, Pilsen, Flaked Oats, or Flaked Corn
they could simply work it out with bmason to have him move that item to their own order. This would be the best solution. If all 10 bags could be claimed and paid for, then there is no problem. If they cannot, the shipping charges go up for everybody else, and the extra bags still would need to be cancelled off of the quote/order.
In the event the shipping charges went up a lot, I would agree with RC0032 about splitting it as a %, but with roughly $22 being split among 40 or so people in the group buy, it is not worth the extra time to calculate it as a percentage ($.50 or .60 per person is not a big deal in my mind).