The cradle is done. The 4×2 spacers are bolted down with 8 good sized batten screws to take the weight of the boat. I might pop in another screw in each corner through the MDF into the face of the spacers. The casters, which keep the cradle about 4 mm above the floor, are each rated for 100 kg. I am sure this will do the job.
The keel is cleaned up and it had a quick coat of epoxy to protect the surfaces from dings and spills during the build.