To fix the delamination I have decided to do away with the split floor bearer and laminate 4mm ply backing planks giving me a 10mm bottom. I will also add rubbing strips to the plank edges on the outside of the hull extending across the internal floor bearers. I'm hoping this will help spread the load from any localised forces on the trailer. I will also replace the old 25mm knees with thicker 40mm knees and instead of screwing the pieces together I will try using stainless bolts and spring washers. I'm hoping this will help me make the boat stiffer and reduce the tendency for the ply to split.
While all this has been going on I have had an extra reef point added to my mainsail and I am thinking of adding a small foredeck just like this one on vivierboats site. This should also help stiffen the hull as well as keep some of the spray out.