Maybe check out the aircraft data plate for the A6M2 below, along with other Japanese data plates that can be found online. The aircraft data plates usually (always?) listed the 'self weight', the normal 'installed load, and the 'full weight load' AS THEY WERE INTENDED WHEN THE AIRCRAFT LEFT THE FACTORY. AFAIK later modifications (either in the field or at modification depots) were not normally indicated on the data plates. I have several scans of A6M series data plates and they show the increase in the 'self weight', 'installed load', and 'full weight load' over their production time frame.
NOTE: AFAICT NONE OF THE WEIGHTS INCLUDE THE WEIGHT OF THE PILOT. The weights of the pilot, his flight suit, parachute, life-jacket, and odd bits he carried with him on the mission do not appear to have been factored in. The Japanese considered the average pilot weight with flight clothes and parachute to be 165 lbs, but when I go through the 'installed load' weights there is no way I can get the weight of the pilot to fit with the values.
On the data plate ;
1. 自 重 = 'self-weight' or 'by itself weight' is the equivalent of the British TARE Weight (no pilot, fuel, oil, bombs, ammo, and no normally removable equipment (radios, gunsight, guns, dinghy, flare gun & flares, miscellaneous bits and pieces, etc) that might have to be changed or maintained between missions, and no equipment that might be expended (fuel, oil, ammo, bombs, flares, etc) during a mission.
2. 搭載量 = 'installed load' or 'payload' is equivalent to the British Removable Load or Weight. This includes radios, gunsight, guns, ammo, dinghy, flare gun & flares, fuel, oil, miscellaneous bits and pieces, etc (ie all the things left out of the TARE weight).
3. 全備重量 = 'full weight load' is the total of No.1 plus No.2, and is approximately equal to what they considered the load for a normal mission (ie full internal fuel & oil, guns, ammo, and all normal operational equipment).
Not on the data plate:
4. 過荷重量 = 'over weight load' you see in the manuals is the equivalent to the British Overload Weight, which would include additional fuel in DTs or special long range tanks, additional oil, maybe additional ammo, bombs (for fighters any bombs appear to be additional weight), etc.
For the A6M the weight of the DT and the fuel it contained would be added to the 'full weight load' to get the 'over weight load'. The same applies to any underwing bombs and such. Here is a data plate for the early-war standard (I think steel) 328L DT carried by the A6M2. I am not 100% sure, but I think the Japanese used 0.735 kg/L (6.13 lb/USgal) for the weight of their aviation gasoline. It was definitely more than the US value of 0.72 kg/L (6 lb/USgal). The 32.5 on the data plate is the weight of the DT in kg.
