With many thanks to Crazy Dave, BobbyFunn, JimInPB and others the stem head on my 170 is solid again! This post was particularly helpful, and once you get past cutting a big hole in the cuddy it's pretty straightforward. Here is a photographic tour of the repair. The soggy, delaminated plywood was no surprise, but the gap above it was: there is 1.5" - 2" of foam and an apparent gap between that and the plywood, which is (I guess) why the screws are 4 1/2"? This tells me an epoxy-fill solution would NOT have worked, as the epoxy would have just run into that gap. The blue color on the rottten piece is the locktite I tried to use... fortunately the piece came out cleanly, and I chose to replace it with materials I had on hand eg. two pieces of pressure treated wood shaped to fit up in the nose. The space itself isn't symmetrical on my boat (I can tell from the fit of the edge rail the hull isn't molded well) but I stuck it in with the same G-FLex I use for crack repairs and filled the spaces around it with expanding foam. The choice of bolts and T-Nuts seemed logical, however the bolt heads prevented the jib furler from moving properly and I ended up having to grind them down a bit. Oops. I figure if the original lasted 15 years this will hold longer than other parts of the boat! I did choose to purcahse a new piece of hardware from Hunter, as the hole where the forestay has been clipped was showing some wear. The rudder top screws are pulling out as well but fortunately the mast tabernacle had been previously repaired and is still solid despite some cracking. I would love to know if anyone (Dave?) knows what is under the jib cleats! Is that also a plywood backing, and if so will it be risky to take those cleats off to repair the cracks around them, for fear they will not snug down again? How many more inspection ports will I be installing?