It appears as though the measurement certificate is just that, a certificate only. May I suggest that a measurement form be developed with minimum, actual and max value columns for measurers to fill in while measuring. This leaves the official certificate to be filled in later.

The method of measuring the overall weight, while the concept is simple, could be quite annoying in practice. Having guidance on how to perfom a weighing, and dedicated fields to fill in for each item (ie. mast, mast tip, boom sails...etc.) would be very beneficial. I can think of numerous ways to do it, some of which could be exploited to make an under weight boat still weigh in.

An example format I like is of the Heron...
Heron Measurement Form