There is actually quite a large CG range where an airplane will fly well. As the wing loading drops, that margin gets bigger. The information about the Sig Kadet was good solid information 40 years ago when written however, things change. With today’s lighter electronics that airplane can easily loose 1/2 pound. The increase in radio adjustments will also help produce an airplane that flies better with a more aft CG. Note that I did not say tail heavy. With a typical wing loading of under 30 oz, most airplanes will fly with a CG in the range of 25% to 35%.