Tony
When I had the boat on the cradle you couldn't move the rubber by hand,even after the autopilot and steering mechanism were removed. I put two wooden wedges at either side of the top of the rudder (stern to bow direction)and chapped them in until it dropped slightly didn't take much hitting, go easy there as you using the hull to prise the top of rudder, I didn't take the top fastening nut off completely just slackened it left about 3 turns of thread, this is to stop the rudder dropping and hitting the concrete surface, I also built wood up (scaffold board cuttings) to about 3/4 inch from the bottom of the rudder to prevent and drop after I removed the top fastening nut. The gator sleeve inside the transom was just loosened with the jubilee clip. I had a 3 foot length of brass bar about 30mm diameter and remove the wood below the rudder at 2 inches at a time and knocked the to of the shaft down, two good hit was enough and the rudder was completely free. Theres a good weight in the complete rudder and shaft so be ready for it, the boat was then raised until clear.
If you require any more info just let me know
Stevie