HughMartin,
I have to agree that only track rcord counts in the end, but the basis of the design is in the regs chosen to be met, and these things are quite powerful in setting the safety of the design.
Automotive examples include anti-lock brakes, air bags, anti-skid electronics or steel belted tires. There is no doubt that the technology of the features sets the baseline safety aspects. This does not make today's aircraft unfit, of course, just resets the value equation, I think.
The site I set up
www.s-92heliport.com has a full set of slides with some systems descriptions and weights and perf. I don't know the stage lengths that you are using, or I could double check your figures.
Regarding belly fuel, there is much evidence that landing on your fuel tanks in a crash is probably not preferable (is that rocket science or what?) The heavy rubberized bags were tested in older helicopters as separate items, dropped without the belly metal structure, and without the pumps and lines and stuff. Nobody knows how the bent metal and sharp edges of a crash can tear the cells and spill the fuel, except that it happens in a fair percentage of accidents in aircraft equipped with otherwise "crashworthy" fuel cells. Because of this, new regs require that the tanks be dropped with the surrounding structure, or that they meet an even higher crash standard. Facing this new standard, the 92 had to put the fuel outside the cabin, where the cells are free to break away, and no sharp metal edges threaten them. In fact, they were tested with the representative sponson structure, to be sure they were unharmed in the drop. Also, the 92 has no pumps, no transfer lines and valves, and no pressurized fuel in the airframe, the engine pumps suck the fuel up. Much fewer leak opportunities. I have posted an .avi of it at (2.5 Megs):
www.s-92heliport.com/fueltest.avi