That's true, Charlie. Measuring at home only has two real purposes: to get the plane at a known safe CG for the first flight, and to have a record of the final flight trim in case you have a crash and want to get the plane back exactly as it was or set up a new one just like it. I keep a file on the computer for every plane I have with all the important data- CG, wing and tail incidence, engine thrustlines, control throws, and mixes. That lets me do good repairs if I need to, and it lets me return to a previous setup if I make a change and don't like it.