Ok so far, now lets assume a ZFW of 61 tonnes, which we load up to with a 'minimum fuel' in the wing tanks of say 3 tonnes. Now I can put 13 tonnes of fuel on (16 tonnes in all) before I gross at 77 tonnes, 12.6 will go in the wings and the rest will go in the fuselage tank - i.e. inboard of the undercarriage and presumably adding to the loadpath as previously described.
Your serve !