Three weeks ago I started to take the floor out, it and the longitudinal stiffeners were crumbling; whilst lying on the floor of the boat I had opportunity to poke about to see how much of the plywood in the transom would need replacing; easy, all of it. the lower half was rotten as was a pyramid shape below each engine drain well 'through transom' outlet. With this much water about, I sat in the boat, stared at it a lot,

then decided that everything had to come out and I would need to split the boat in two to get to the transom. You simply pull out the rubbing strip, unscrew the aluminium strip, take out all the screws that hold the top moulding to the hull and pull. It is not glued together at all! This may change when I put it back.I hit a problem with the transom, and had to saw the only glued section, where the engine bolts on,from within the hull, this took 40 hours of sawing/ chiselling/ prying etc.Not so simple.
The boat eventually parted and I could start removing the transom plywood reinforcement, the topsides have been moved forward for easy access.
This is the transom. From top to bottom- just grey resin paint on the inside, then 19mm of ply, one layer of chopped strand mat, then another 19mm of ply which was bonded to outer grp hull. Part of the ply was good as new, another 20 hours of careful chiselling.
To get the floor out I machine cut around the joint between hull and floor which is more 19mm ply. Judging the depth of cut is tricky, I did stop and make sure I wasn't going right through the bottom of the boat once or twice. 19mm marine ply on order.