I weighed my two oldest sting mains. The oldest, a UK kevlar tape drive weighed in at 27lbs. The second, which is newer (I think Bob Rutsch said it was a 2004 - 7 years ago) is a UK carbon tape sail that weighed in at 25lbs or 11.3kg. I'm pretty sure my newest sail weighs more (although I didn't weigh it because it is stored at the sailmaker).
My newest sail is not the most expensive that my sail maker offered at the time. As I've shared, my sailmaker said that the more expensive sail would have weighed less than my current sail. Too, he recommended a sail weight of 9-10kg (by comparison, my sail weights listed above are based on roughly 11 and 7 year old technology).
Thus, allowing for a little technological advancement in the last 7 years, I'm going to submit my rules change request with a sail weight of 10kg as follows:
The Main shall have a minimum weight of 10kg, excluding battens. The intent of the rule is that all sails submitted for measurement will be constructed using well establish sailmaking techniques. The class reserves the right to reject any sail with additional weight added to the sail that is determined to be there for the sole purpose of meeting the minimum weight.