400 Freighter
 

Can anyone tell me why some B747-400F's have a sliding ZFW/TOW scale......i.e. smaller ZFW's mean larger TOW's and visa versa?????

Yes.

Otherwise, too much weight in the fuselage, and not enough in the wings. The wing bending moment is then excessive.

Are you refering to Extended ZFW (Variable ZFW to our US colleagues)?

standard mzfw is around 276000kg

above that, you have to check the mtow as it is decreasing due to wingbending. When using increased zfw , forward max cumulative weights will decrease as well.

Max increased zfw is around 288000kg