UIM measured length - how long is your boat?
For racing classes, the length that is important is the "UIM measured length". This may be different to what you think the length of your boat is, and will almost certainly be different to how it is named by the manufacturer.
For RIBs the measured length includes any bow overhang, but excludes the tubes where they extend beyond the transom.
In practise this means that for events such as the Offshore Marathon races, although the minimum length is 7.35m, you would probably need a RIB with a nominal length of at least 8m.