Got your answer for you: "The balance range for the Ultimate is 1 1/2" to 1/2" from the leading edge (front) of the read cabane - without fuel" That is published right out of the book. I built mine with an OS 1.60 and Tru-Turn Ultimate spinner and started the CG right at the 1/2" measurement point for starters. I found it to be a bit nose heavy and couldn't get the plane to float in during landings but had to trim with up elev. to maintain a flat attitude. Moving the CG back to the LE of the aft cabane has helped with all aspects of flying my plane, including those landings that cushion themselved in ground effect.