Or another way to do it is to use Runaway guns technique but only make the correction at the mid point. That way the correction is always twice the angle.With 10 degree drift lines students seem to be able to work out how many degrees they are off track. (if you have long legs split them up into 50-60 mile lengths)
Then if you are 6 degrees off the correction is 12 degrees. If you are 4 degrees off the correction is 8 degrees.
I've nothing against SCA (whichever floats your boat and it works). With the SCA method you need to know how many miles you are off to apply the sca then determine your closing heading , then apply the new track. And how do you know when you have regained track.
(but that doesn't help you answer the CAAs questions)