In a normal (not ALT 1 or ALT2) dispatch, T/O performance charts assume the CG to be at the worst position (FWD limit). Every time your actual CG is behind the FWD limit, you will have excess performance both for accelerate stop as well as for accel Go, even if your TOW=MTOW. If you want to use this excess performance to improve your TOW limitations, you must use certified procedures ALT 1 or ALT 2, which no longer assume the CG is in the FWD limit, and the loading has to be done is such a way so not to have a CG forward of the new limits for ALT 1 or ALT 2 as applicable. Actually, taking your CG AFT of the FWD limit improves your TOW capacity. This is applicable to the 767.