Worth a try. I have never been able to get stains out at all.
I now laboriously (well, not labor if the sun is out) lower the new mainsail and genoa every few months and go at any dirt with Fantastic and a scrubber.
The dirt is from contact with lazyjacks, from the flogging of the backstay against the roach, from the spreaders where they touch the sail, from the boom if I allow it to get dirty, and from the sail cover (if it gets dirty).
Mildew is a constant issue, and very hard to remove even with straight Clorox.
However, mildew grows only in dirt. So, no dirt, no mildew.
Keeping new white sails white is much more effort than anybody is willing to admit.
Dacron is impervious to almost everything. But white, well, that is a temporary condition and one which we struggle to maintain.
Oh, something else roughly on the topic:
Do you notice stitching coming apart even on new Dacron sails?
That is inevitable, too. Synthetic sails are so hard that the thread doesn't bury, as it did in cotton or canvas.
It lies on top. Abrasion is inevitable.