I am trying to find data on fuel flow figures for various airplanes (various sizes is all that's important, not type) with everything held constant except longitudinal CG position.  I know that performance increases (decreased fuel flow) as CG is moved to the rear limit but I need to quantify this effect.  I have considered running simulations on a certified airline sim but according to an A320 check pilot, they find performance errors in the software all the time (because the main purpose of the sim is to practice emergencies).  If anyone has any insight into this and any suggestions or contacts, please let me know.  Thank you!