recoring from the inside
I have done some recoring work from both the inside and the outside. My experience is that recoring from the outside is easier, except that the finish work can take more time than you save with the fiberglass work if the area is small to moderate. If the deck is already painted, going at from the outside makes all the sense in the world because it is easy to match paint or repaint the whole deck. If you have original gel coat & molded nonskid on the deck the choice is harder. Work from the inside can typically be concealed by the headliner so a perfectly faired job is not necessary. To work from the inside, wet out the area with epoxy, then glue in the balsa with epoxy thickened with silica. A generous amount of thick epoxy should be applied the center of small to moderately sized balsa sections and pressed into place until epoxy oozes out the sides (Clean up with a plastic scraper). Brace in place using a piece of thin ply (covered with plastic) & numerous cheap pine battens from the local lumber yard (flexed into place). Laminate each fiberglass layer from the inside by wetting out the area and then waiting util tacky (e.g., after 30 min for 60 min pot life) and then pressing precut cloth sections into the tacky epoxy. Use a roller to eliminate voids and then paint on fresh epoxy for the next layer or finish coat. Use staples (remove as each layer kicks) or thickened epoxy if you have area that are problematic.