BEagle
Whether you apply SCA and drift error or just SCA, the number of numbers to be dealt with remain the same.
FWIW, your geometry only works if you apply the drift error while getting back on track. It matters less only because the correction is so coarse for larger SCAs that continuing to drift happens for such a short time. If you envisage a 360 kt scenario with a 10 degree SCA and a 10 degree drift angle, applying only the SCA will simply parallel the desired track.