p1muserfan you may be mistaken as the 27% you speak about is NOT actually the CG... that is on "take Off" and usually it is always between 44-47%  and yes there you can insert the right value... as for getting this info accurately, Fspassengers will tell you everything you need right after loading all passengers, cargo and fuel... it will also tell you the ZFW.. everything together in a report! very good! and this add-ons is not expensive at all for what it worth's...   otherwise try what Rupes's idea.