http://www.rotdoctor.com/glass/GLrotrepair.html
great reading. deck surgery.
i did do a semi self invented method on a small area last winter, next to wildmans boat, but it abutted a rear hatch and had a couple cross saw cuts on edge of hatch that were never filled except with paint and they rotted the surround core area a few inches back. had access to dig out with a screwdriver from edge, and went to good wood and drilled 2 holes. allowed to breathe for a few days. used system3 epoxy and filler, blue tape on edges. gelcoat touch up to screw hole(after 2nd epxoy application to fill hole). i used a disposable tube in a gun filled with epoxy/filler to get main push, and then followed with syringes taped to the couple holes to gravity feed more in. did not do vac method beacuse had exposed edge. had to wipe excess from edges and reapply tape until kicked, so was a bit messy on edges, triple up on gloves. also at 2am fell outta the boat when ladder skidded, almost took myself out, lesson learned no more late nights solo! worked great, area is solid as heck, and gel coat blended in with alwgrip deck on screw holes.
this winter have a mid deck soft spot next to t-top to deal seems contained in area, and prob will do the URLlink method-drill holes,acetone,vac,dry by compressed and natural air,CPES,vac, thicker epoxy flexible attribute,vac,gelcoat spot touch.
nice thing about my decks is the glass thickness, and glass on underside as well, someone way overbuilt these decks.
forward fishbox has no core its gone, prob have to cut it out and recore, i am considering doing a thickened epoxy injection method and a hole pattern, with vacuum, and judicious use of blue tape to create vacuum over open holes. whichever do, its a crappy place to work. one of those jobs nobody wants to do even for money.