10.3 - 8.5 = 1.8, which is close to the 1.7 underweighing error reported in the original post. Maybe the solution, until we can find a better portable scale, is to add about 1.75 pounds to the Berkeley reading. However, the underweighing error may not be constant throughout the range, so a 40lb. wsb may be underweighed by more than about 1.7 or 1.8 lbs by the Berkeley scale.