- "What I still don't get is Rob saying there is no way beams on an Atlantic or Pacific would be lighter than on his craft due to lower forces at play. To me it still seams its based on weight, and where it is located."
Take a simplified aspect of weight and where it is located.
In an Atlantic proa the windward hull will weigh at least the same as on a Harryproa plus the weight of the rig. When the forces on the sail are sufficient to lift the windward hull out of the water, the greater weight of the Atlantic configuration will put greater stress on the beams than for the Harryproa. This is ignoring the greater stress due to torsion loads.
In the Pacific proa configuration, when it is caught aback you have a similar situation as the Atlantic proa - accommodation-hull weight plus rig weight being lifted out of the water. Although some Pacific proas may never be caught aback in high winds, the beam strength required needs to assume that this might happen on safety grounds especially offshore.
In both Atlantic and Pacific proa configurations the beams will need to be sized for worst case scenario - hull being lifted out of the water.