Mildew (and most related fungals) are best removed from non-painted surfaces using STRONG alkaline / caustic detergents. Such will dissolve any cells that have penetrated into the surface of the material.
One of the best such detergents available in your area (usually available in local marina shops on the Chesapeake or by special order through WEST MARINE, etc.) is called "Tuff-eNuff" a sodium silicate based detergent available in spray bottles. Tufenuf.com - (expensive). If you cant obtain Tuff-eNUFF, then use TrisodiumPhosphate - TSP.
Oxalic crystals and TSP are available from most PAINT and hardware stores. Rinse thoroughly between each step and wear rubber gloves, goggles, etc. with both of these chemicals.
Spray and soak the mildew with the strong detergent so that it dissolves; then thoroughly rinse with water; THEN use Oxalic Acid and apply to 'bleach out' any remaining staining and 'shadows'.
Dont MIX caustics with Oxalic Acid. You have to remove the cells, before you oxalic bleach .... as if you leave any dead cells, they will only become the nutrient source for other specials of fungals.
Dont use on wood, painted/varnished surfaces, or 'natural fibers' such as cotton, rayon, or wool.
I dont think you will want to use MEK on a vinyl head liner ... it can dissolve the vinyl.
If you have mildew inside the boat, Id suggest you do an extremely thorough job of mildew removal, including from all the hidden 'underspaces' of the sole, the bilge, the anchor locker, and the vent line on your water tank!! --- its spreads by airborne spores and you really have to kill the spores at their source to keep it under control. Wear a respirator when cleaning mildews and fungals, and alway 'soak' it before disturbing it to keep the spores from 'flying about' - as some species of fungals, especially the 'black species and their spores' are VERY dangerous to human lung tissue.
here's a repost of a more detailed use of such caustics/oxalic
.... Oxalic Acid is also good for removing the brown staining on the hull/bow and dacron sails from tannins in the water, also quickly dissolves 'rust stains'.