CoffmanStarter, MAA regulations appear to ape EASA terminology, in the adoption of 'Acceptable Means of Compliance' soft law. EASA AMCs are non-binding and hence 'should' is correct - AMCs do not use 'shall' or 'must' as Alternative Means of Compliance (AltMoCs) can be raised by a MS as they wish.
AMCs are not a concept used in the UK Air Navigation Order, in which only 'hard law' mandatory regulations are included.
In more sensible times, a military document would use 'are to' for any mandatory regulation - adoption of EASA 'soft law' terminology must be rather confusing for many who are more used to military orders.