I'm not sure what you mean by suitable ....I always thought the IET or someone like that had calculated that the armour of 2 core is always suitable unless you delv into larger size swa ....
.... with any type of cable, there is (in relation a particular installation) always going to be a length beyond which a cable of a particular CSA does not result in a low enough Zs for ADS. That's no less true of SWA than any other type of cable, but with SWA (using armour as CPC) there is the added complication that if Zs is 'too high' (i.e. cable too long), not only will the requirements for ADS not be satisfied in relation to L-CPC faults in the load, but also L-armour faults (e.g. garden fork through it!) in the more downstream parts of the cable - in other words, the 'earthed armour' will not do its job properly (won't necessarily result in disconnection as quickly as the regs require).
Kind Regards, John