Thanks for the link they were one I hadn't heard of so didn't check. Sure enough they have Columbus and decent shipping rates ($14 like you said) to boot.
Are you saying 2 packets per 6 gallon demi or 15 gallon demi? I was thinking 2packets of yeast per 5.5 gallon batch would be about right, mr. malty suggested 14 packets of yeast.
If its the 11g packages, then one per 5.5 gallons is plenty.