I find the center of gravity topic to be peculiar simply because manufacturers go out of their way to design the camper to have the ideal center of gravity but then all of the holding tanks are typically in the back of the camper. As an example, my fresh water tank sits at the very front of the camper and with 40 gallons weighs 333 lbs. However my holding tanks are pretty much over the tailgate meaning my center of gravity is going to vary widely just based off where my fluids are. I suspect most other campers are similar.
Back to your question at hand, is finding the COG of particular importance or are you just curious to know for knowledge's sake?