Hey Dale, on my regular size scorpion I have the cg at 165mm from the leading edge at the root. The cg is right on the back side of the main gear leg. If you check this link at altecarerc http://www.altecare.com/scorpion.htm they mention having it at 150-160mm as the original recommendation is too far forward. Even 160mm I found to be not enough so I moved it a little further back as others I know have! Any more than that and the airplane would sit too light on the nose wheel even with a full tank.

Mike