Basically the setup would appear to be more or less the same as for many British bikes, that the crank/piston position needs to be set to where the spark should occur, the AA unit should be secured with the retaining bolt *just loose enough to turn it on the taper*, and the points plate should then be fitted in the middle of its range of adjustment with the AA cam set in a position where the points are closed.
The AA unit should then be slowly rotated on its taper (without moving the spindle) in the normal direction of rotation until the points *just* start to open, and that should be the position it needs to be tightened down at.
Once the AA unit retaining bolt is fully tightened the ignition timing can be re-checked and fine adjustment done by moving the points backplate.
Normally setting the ignition timing on Brit bikes involves locking the AA unit at full advance and the crank/piston position is also set to the full advance position but the Crusader would seem to differ in that a retard setting is given (by Roy Bacon info -what does your BMS book say?).
So I would expect it to give some info on how to at least set the correct ignition timing position?
It is possible that in this case the AA unit should not be locked fully advanced (so is set retarded). And that the retarded timing position occurs slightly after TDC (0.015") instead of slightly before which is generally the case?
But I must stress that what I have said is mostly guesswork based on the procedures for other British bikes, so proceed with caution (or find somebody who actually knows for sure).