Calan, that's a great chart and obviously a lot of work, thanks for the info; however you'll have a heck of a time trying to quantify "hardness" for the different planes unless, as you suggest, HT provides some numbers. Most of your numbers like climb rate and acceleration are empirical and can be easily quantified, but how are you going to account for an aircraft with weak wings but strong fuselage and good pilot protection versus the reverse if all you do is shoot each one in the wingtip as suggested? I'm not sure where/when I read it but I understand each aircraft has hit zones which vary in damage required to destroy it. If this is right, all you'll really know is relative wingtip hardness. To do this right you'd have to divide the airplane up and test each section and that would be a very laborious task. If this is what Krypto has done then kudos to him, that'll be very nice info to have.
An alternative idea would be to go back to the subjective measurement and take a poll of the experienced guys in AH to see what they think are the toughest (i.e., most damage resistant). For instance, in my opinion, I'd seriously disagree with ranking the Hurricane a 3 for damage resistance. It's much tougher than that and at least equal to the F4U that you've ranked a 5. I'd also say that both the F6F and F4F should both be rated a 6. I've had several occasions to hit both of these with 20mm only to have them fly away with no apparent damage (i.e., no smoke, falling parts, etc.) which is very unusual while I've never noted 109's as being anything other than average to below average in toughness (especially the empennage) so I'd rank them a 2-3 because they're almost always a one-shot kill. Same with the 38, one long-range shot in the empennage or a tailboom and they're done while the inboard wings are fairly tough.
EDIT: forgot to mention that a poll should ask what type of weapon (20mm, 50cal, .303, etc.) they get their most kills in, it'll make a big difference as almost no airplanes will stand up to more than a couple of 20mm hits so all airplanes will appear much weaker than if you typically fly a P-51.
These are just my opinions, I'm sure many would probably disagree with my examples but that's the point to the poll, opinions would even this all out.
Mace