There is a process we did on a soft spot on the deck of our boat, a little over a square foot. Drilled 50-60 small holes, filled syringe with some kind of resin and let it do it's thing. I know it's kind of a band aid but was worth a shot. That was two years ago and the spot we did this to is solid once again. Might be worth a shot. If it doesn't work, you'll be cutting it out and replacing it anyways! If you want more info, shoot me a message and I'll try and find the link/video.