MM is a-gain right, but don't tell him i said so; i wasn't sure if it was 5400 or 5600(and was tooo lazy to check); so i erred on the right side i think....
i will question whether gear is at 5k; i all ways thought it was durables/metals/hards at 5k and wearables/synthetics/softs/lines (whether round line or flat line/webbing) at 5.4k synthetics; naturals disallowed; kinda assuming that the extra was in the spirit of stretch/wear/flexhaving fluctuations and losses for the non-durables?
i've lost my copy of the Z in a move a year or so ago; or at least it hasn't floated to the top yet! But, i think the spirit of the Z; if not the literal verbage is that the 'loop' not the cord itself shall/will/whatever meet the rope/synthetics tensile requiremeants. So; i go with what MM said; but once again; please don't tell him!
In any case, on a 5.4kk line doubled over with your weight on it ye are pretty safe; just as on a 2.7k cord doubled over; on 1 leg of the 5.4k line (meaning only half your weight on that leg of line attatched to the doubled over 2.7k cord) ye should feel confident personally, if not legally; let alone half your weight on a doubled over /basket position 4.4k.
But really it isn't a straight basket, but a leveraged/bent/angled basket for some loss; but then the 5.4k tautline attatchmenat would not be so much a 5.4k x 100% linear, but rather 5.4k leverged/choked/5.4k X 80% linear. Not to scare ya, but give more proper imageries to carry over to other analogies and engineering that we get ourselves into. So, really, really, we been there, have questioned the same things; and are looking out for ya.