From what I understand the Camarillo Zero's cowl is actually the same size as the original Zero cowl however there were internal components altered to accommodate the slightly larger P&W engine and again from what I understand the size difference is nominal. Eric might be able to get info on that as he's a regular around that aircraft but from what I read about the two engines the difference in diameter is about 3 inches. C/G issues in minor structural mods are usually non events and many times are easily remedied by using ballast in the nose or tail, if even necessary. As a matter of fact sometimes ballast is necessary to compensate for obsolete wartime equipment (mainly radios) removed during the restoration.
I don't believe the Zero was first aircraft to incorporate aluminum (or duralumin) skin as a structural member. I can recall portions of the DC-3 that had skin carrying a structural load and were repair sensitive if damage was over a certain size.
The latter may be true. I only know that Jiro Horikoshi's design team had tried and failed to design on paper an aircraft capable of meeting the Navy's specifications due to weight until Mr. Horikoshi had the idea, presented as independently derived at, to incorporate the aircraft's skin in the design itself as a structural component. I think arguably the Junkers J.1 was probably the first aircraft anywhere to incorporate this idea - though very differently. But that's not the only instance of problem solvers independently arriving at similar, but not copied, solutions: another example being oblique firing cannon.
Someone also mentioned earlier that the Zero's controls "turned to concrete" at high speeds. True. I've heard it cynically stated that Kamikaze pilots would often have been unable to pull out of their dives even if "sense" came to them in their final moments. I know that, at least for the Japanese, rigidity in the control cable system was a required priority in aircraft design - until the Zero. Horikoshi's problem with the new aircraft was its unprecedented speed and the fact that as its speed increased there was a dramatic increase in the sensitivity of its controls. This was discovered during the A6M1's first test flight, along with vibration problems due to the two blade propeller (which was then switched to a three bladed variant). The rigid control cables of the prototype were replaced with cables that would 'give', and that solved the problem: as wind resistance on the control surfaces increased, the give in the control cables compensated, and the pilot did not experience the over sensitivity to input previously suffered at higher speeds. But what Horikoshi did not mention was how that solution impacted control at dive speeds. "Concrete" is thus an apt description for it.
All of this highlights some of my original point regarding Japanese philosophy and how it was independent of limitations posed by technology or economics. I understand that accepted theory, in the West at least, states that the Japanese merely made do with the best that they were capable of producing, maneuverable but under powered Zeros being in part the result. But I (obviously) disagree. Japanese aircraft were designed and produced for the offensive, and their doctrine emulated that as well. The Zero wasn't designed with armor plate in part because theoretically it would never be within enemy cross hairs to be hit in the first place. Yes, some of that was based upon pragmatic considerations of how armor would sacrifice performance, but there was also an element of uniquely-Japanese confidence within it. Why should the Zero ever need to escape a dogfight by diving, when it will rule every opponent it faces? These men typically refused to wear parachutes until late in the war, when they were ordered to - even then often using them only as seat cushions. Such wasn't fighter pilot bravado - it was indicative of a culture that permeated design boards and industry as well as the men at the front. A Japanese pilot was expected to maintain the initiative or fail, to fail meant death, and their equipment was designed with that idea in mind at the expense of everything else. Were they "fragile" machines by Western standards, incapable of taking hits? Absolutely. The Americans didn't nickname the G4M the Flying Lighter without good reason. But these things were not regarded by the Japanese as design faults until after the fact, when losses mounted and the fate of their culture demanded that they rethink their original ideas and adopt designs employed by their more successful enemies. To judge an aircraft like the Zero fairly, I think it should be seen at least in part through the eyes of its designers; in that it did exactly what it was designed to do, exceeding all expectations, sacrificing only that which was considered expendable.
The Japanese did not largely dispense with using parachutes because their industry could not manufacture them, and when the Japanese wanted to build heavy fighters with powerful engines (like the Shoki and the Raiden) the Japanese built them, and they were good machines. Thus the Zero was a product of a philosophy - not technological or economic frailty.
Ron Cole
But it was glorious! I sat in the Raiden, too, thanks to Steve Hinton and a screwdriver - before Ed Malony had the cockpit of that aircraft spray painted metallic green. It was still all original Mitsubishi 'bamboo' at the time. My last visit with that bird, which is my favorite aircraft in the world, revealed the extent to which the spar cap exfoliation has taken its toll. Even in 1987 Steve warned me not to "move around too much" in the cockpit for fear of landing gear collapse. But short of a full and expensive restoration there is little that can be done. 
