Someone mentioned using the firewall to keep the numbers positive. That only works on a taildragger. On a tri-gear, anything forward of the firewall is negative. Select a datum, even beyond the nose , spinner, whatever, of the aircraft and your numbers will always be positive, whether it's a Cub or a 747.
Larry Flesner I did just what Larry said, I placed the datum ten feet in front of the center line for the main axles. All moments and weights are always positive that way regardless of where you move stuff around. The arm/moment for the mains will always be 10' x the weight of the mains no mater what. easy math Mike Turner 1n1 Edgewood NM
