I don't quite understand what's so controversial about a pressurized hull providing more rigidity: the atlas rockets from the 1960s that literally launched the US space race relied on it. That design solution provided stronger/more rigid hulls for less weight.
http://en.wikipedia.org/wiki/Balloon_tank
Now, that doesn't mean that it's easy to pull of, or even dangerous. But it's been successfully done 50 years ago in extremely demanding environments. So why not.
None of us are doubting that pressurized hulls can provide rigidity in some situations, merely whether they would work in a racing yacht which is in a very different situation.
Personally, I love pressurisation in the right place (ie my bike tyres, which are at very high PSI yet remain vastly more flexible than any boat) but not in the wrong place (ie excess pressure inside my windsurfers, which can blow them apart AND make them more flexible). So it's not bias against pressure.
As to balloon tanks, well, I'm no rocket scientist, but the situation seems very, very different. The balloon skin tanks are cylindrical, which is a good shape for a pressure vessel; they were (according to the net) .048 to .015 of an inch thick. They were so thin that the rocket was normally stored at 90 degrees to its operational angle, always had to be pressurised, and had so little impact resistance that there was at least one instance of a rocket blowing up after a mechanic dropped a wrench on it.
No practical racing craft is going to have such a thin skin, because it is always subject to impact loads from small objects in the water. No practical racing yacht can have such a thin skin, because there are crew running around it. No practical racing yacht is a complete cylinder, so somehow you have to build in a means of retaining a proper hull shape.
So you're going to have to have a heavier skin to resist such loads, which means that you will surely lose the benefits of the thin skin that was the raison d'etre of the balloon tank.
Ironically, I was reading JE Gordon (prof of engineering) last night and came across the chapter where he was dealing with the explosion of pressure vessels. It was interesting to read how the fitting of gussets and frames (which would almost certainly be necessary to handle the keel and rudder loads, rig loads, fitting loads, winch loads etc) can destroy the structural integrity of a pressure vessel. Doesn't sound like an ideal way to save a few kg.
Let's note - inflatable sailing craft have been created. I've sailed a couple. At practical pressures, they were god-awful because the pressure was inadequate for rigidity, and that was on windsurfers were rig tension is not an issue. One practical and reasonable-performing inflatable cat did quite well in the UK, but it had to have extra "streamlining" added on to the cylindrical hulls and it suffered from lack of rigidity, therefore it was not a great performer.
Doug, as Paul noted, there were many other ways to reach measurement trim that would not have changed the performance of BMWO significantly.
