Corrected Parker model 2500 Gravity Wagons

Parker 2500 gravity wagon weight correction

- Checked the Parker 2500 mod XML mass values.

- Original empty mass was about:

•   - 3,500 kg
•   - 7,716 lb

- Found the big model empty weight should be about:

•   - 2,500 lb
•   - 1,134 kg

- Updated empty mass to about 1,134 kg total.

- Kept the component weight split proportional:

•   - 648 kg
•   - 324 kg
•   - 162 kg

- Estimated 12,334 liters of corn weight using 56 lb/bushel and 1 bushel ≈ 35.24 liters.

- Estimated corn load:

•   - about 19,600 lb
•   - about 8,890 kg

- Corrected loaded max mass to match approximately:

•   - 2,500 lb empty wagon
•   - plus about 19,600 lb of corn
•   - about 22,100 lb total loaded weight
•   - about 10,025 kg maxMass

Credit for Rooster Mods for the great wagons!