Following the recent CIAM Plenary Meeting, there is a correction to the F3M rule containing the formula for calculating the permitted tolerance that appears in the 2007 edition of Volume F3A of the Sporting Code.
The corrected formula is:
5.L.1.3 d - General Characteristics of a large R/C Aerobatics Model
(D x s)*0.9 -0.5 <= d <= (D x s)*1.1 + 0.5