Early in the war, I've found that if you can keep your bow pointed towards the Flower (minimize your silhouette), with a decent deck gun crew - or doing it myself - a few hits and the Flower turns away. This masks their single gun forward, and I can usually plug away at his stern and sink him before the aft machine gun does any damage.
Of course, for anyone working on GWX 1.04... please disregard this thread... the Flowers are tough foes