That is the datum given to us in our manual and there is a reference point as i mentioned earlier , the trimsheet looks like any other trimsheet i have prepared for many airlines with a slight difference in that this has indices for the deadload instead of the scales to trim the deadloads , i will definitely scan the trim chart since i dont have the knowledge to ellaborate further
as far as the exercise is concerned it is definitely no waste of time or dogs breakfast as you put it since it is only a script which actually greatly simplfies (so far) with 100% accuracy that which is being done manually and seems to be working , all the airlines i've dealt with so far have used MAC on their loadsheets and MAC to determine the T/O stab trim settings so i wouldnt know the difference,but i'll do the scan first