Not sure for what boof is striving, but, trouble is, MacB, if it is for aviation trim terms, the variables are not linear, hence the need for complex equations for the 'curves'.
For aircraft (737-400) trim, the datum C of G is determined from the value of the fan of lines in the graph bottom right on
http://ahmthy.com/AHM560/B737-400/TH...DTRIMSHEET.pdf and from this value the trim setting is determined for a specific flap setting.
It was while putting that fan graph into Excel where my brain hurt.
