Here I've removed the original fiberglass patch and sanded down to the epoxy layers I laid from the bottom. The area has been painted with epoxy resin in preparation for new layers of fiberglass to go on top. Also note at this point I pulled the entire floor up because I found unacceptably high moisture readings everywhere. The remainder of the balsa core appeared sound and didn't feel wet. After just 24 hours the moisture meter read 0% moisture everywhere.