Regarding the original poster’s comments, large aircraft often have 2 maximum weights the pilot must not exceed; Max Gross Weight (MGW) and Max Zero Fuel Weight (MZFW). I’m not aware of a light GA aircraft that has a MZFW limit.

ZFW is the weight of the aircraft plus any payload carried in the fuselage. MZFW is the max an aircraft can weigh minus the total fuel. This weight does not include the weight of the fuel or wing stores (weight of tip tanks or in military aircraft, weapons on wing pylons) because their weight is supported by the wing as the original poster referenced.

The P-3C aircraft I flew in the Navy had an empty weight of 70,000 lbs, MZFW of 77,000 lbs and MGW of 139,760 lbs. So... the max payload we could carry in the fuselage was 7,000 lbs. All weight above 77,000 lbs had to be either in fuel or wing pylon carried weapons. The weapons carried in our bomb bay also counted towards our MZFW.

I hope my example helps to explain some of the original poster’s questions.

Todd