Jason,

My reference was the same line, except further back on the fuselage. Near as I can see it's the same line as the one you're describing, except that it's from white to purple instead of from yellow to purple. The stab is zero to this line, and the wings are 0.3 degrees positive to this line. Out of the box the wings were 0.3 degrees negative to this line.

Also, it's true that measuring the stab is difficult because of the full width elevator. What I did was use the seam on the tip of the stab as reference line and measured to that.

The lateral CG isn't out by very much, but a peso probably doesn't weigh very much either. I'll try adding some wing tip weight to see if it helps.

PS-> They use Pesos in Argentina don't they?