I think John said it best.
1.2.1 The maximum overall length measured on the hulls is 5.00 m (= 16.4 ft).
7.3 Overall length of the hulls
The overall length of the hulls, outside rudder pintles, corresponds with the horizontal distance between the verticals passing through the extremity of the hulls, the boat being levelled on its waterline.
7.4 Rudder pintles
Elements fitted to the sterns that only function as hinges for the rudderblades or rudderstocks and don't effectively lengthen the waterline of the platform in any way.
The way I read that, is that the gantry would have to be defined as rudderstock to be permitted?
