Ron, here's the way I do that. some stuff can only go in 1 place, like the strut and rudder, mount them. load all the stuff into the hull that will go along for the ride, motor and mount, tube and shaft with the prop, the tanks and the tank mount, radio box with all the stuff in it. what I mean is you can move most of that stuff around, and you must load the boat up like it will run to get a proper balance point. with everything in you can scoot the engine and the radio box around until you get the balance right. my c/g is at 9 5/8" from the transom with no fuel. You must get the balance right with the weight of the parts that you must have or the only other choice is to add lead when it's done. I don't mean to insult your smarts, but I've seen more bad handleing boats because everything was put in a convient place rather than where they were supose to go. In my opinion the faster you go the move the c/g must be moved forward to fight the areo lift, or something like that.
Mike