Thanks a lot for your replies , I am just interested in fuel efficency and became interested in tail loadings. I can't find any data from boeing on what sort of fuel savings come with each percent MAC so thought I might try and look at it practicallly and esimate it myself. The loadsheets I have don't have FS so I am not sure of the distances involved for the moments.
Pretty much stuck really. The info I'm after at the end of the day is really the advantages gained between an a/c the way we load now and the same a/c loaded with an aft c g.
Anyway, thanks again, I'll keep plodding along! Cheers.