if PG opened fire at 5:55:20, she had all time to fire 2 Vollsalve (spotting the fall of shots) + a Gabellgruppe of 3 semi-salvos by 5:57:15 (fall of shots at around 5:57:45).
Therefore PG could have switched fire to PoW at 5:58:15 and fired the "ranging" salvos by 5:59:20, spotting fall of shots at 5:59:45 and starting rapid fire (at salvo 5) at 5:59:35. Then just other 3 semi-salvos. I assumed PG always fired semi-salvos, never broadsides.
This timetable matches both Antonio's battlemap and Jasper account. The only thing that does not match is the "switch fire" time to PoW, that the PG battlemap puts at 5:59.....
However 5:57 looks quite credible as Lutjens could not allow PoW to hit Bismarck undisturbed after 5:56:30, when salvo 6 from PoW hit for the first time his flagship. In any case 5:57 matches with Jasper count of salvos, 5:59 does not.
"It takes three years to build a ship; it takes three centuries to build a tradition" (Adm.A.B.Cunningham)