An update. We have decided to try to get the boat back in next year. Much to do and have begun the recoring work around the keel. The rest of the boat's dry now, deck, hull, transome, cabin top, ..., but I can't get around the keel to dry out. Gravity I suppose.
Plan to follow the steps used on Brass Monkey above. Half the floor is up. The floor's balsa core is the consistency of cardboard at best on down through mush, all the way to dust. Am trashing the floor and will build a new one. Been carving into the innner skin and balsa around the keel. Hard work, but it's coming along.
Will recore with Core-Cell. Expensive, but I won't have to do this again. It's not as strong as balsa so I dug into the Scantlings calculations. See if I needed to beef anything up to compensate.
The keel sump is bonded in with enough glass to meet open ocean Scantlings without the core. The thick inner skin is a lot wider than required. Guess that's why my keel is solid even though much of the core around it's about as strong as oatmeal. Suppose I also have a good idea where some of the missing weight came from in a J29.
So, I plan to replace the thicknesses that were there with biax, epoxy and Core-Cell. The verm is all headed for the trash. Not as bad as some I've seen in J24s, seems like more resin less verm, but nasty just the same. Will replace it with stringers to set the new floor on.
Will post some pics of my boat's "basement" in a short while.