I have to argue for the carbon mast on the T. Like someone said on that thread (no, I have not read it in a while), instead of buying several extrusions and testing them to find the best/most suitable, have a mast built like you want/need and be done with it. A team can have a mast(s) tailored to suit their needs and the bend characteristics and quality can be more tightly controlled.

As far as narrower and lighter goes... If you build a lighter boat, then less hull volume is required b/c the weight of the whole package goes down and requires less displacement. So, if you keep a similar volume, more of it will be in reserve for when you need it. Also, with a lighter boat, the crew then becomes a greater percentage of the total package weight and has more control and effect over the center of gravity. On the con side, weight aloft becomes more of an issue too (pitching). As you go to the heavier wider boats, it's not just the volume in the hulls that is keeping them up. Since you have more beam, the crew can get further away from the bow and has more leverage (fore and aft) against the platform to keep the bow up.

W