Hi Lloyd- The soft spots on the side decks were very obvious. Spongy when walked on. The foredeck was a little less obvious, but it too was springy. I mostly tapped around with the butt of a screwdriver and listened for the dead spots.
What I found was that there were large areas of the side decks that were completely rotted. Then there were areas that were wet, but still sort of sound, and the top skin was bonded well to these areas. The delaminated areas were in the worst areas of rot only.
I ended up removing all of the side decks and foredecks since I figured I would go ahead and fix it all while I was at it, and I was glad I did. I only found one or two small areas where the core was actually dry. The foredeck was totally rotted at the bow end, extending about two feet back, then it turned solid (but wet) in the middle and more rotten towards the toe rails.
I was very surprised to find just how wet the core was. I figured it would only be wet in the rotted areas.
And yes, its a big job if you have to recore. It's difficult from below due to the liner. And it takes forever from the top. I am still trying to get it ready for paint. Should be priming on Sunday...
Good luck with your decision. May be worth hiring a surveyor if you have any doubts.
Doug