A couple of thoughts ...
(a) a 744 operator did a study several years ago looking at a revised fuel use schedule to constrain the cg closer to the min trim drag case and found, in the payload limited region (ie extreme range) that they could pick up a couple of extra passengers with the fuel savings ... not to be sneezed at over the year's operation.
(b) so far as loading systems go, unless you go to the trouble of weighing everything and doing the sums in much more detail than is often the case, then the end cg calculation will be in error to a greater or lesser degree .. and the stab trim setting with it.