There is not a specific plan as it depends on what you are using to support the boat. The cradle I use has 3 supports either side and the keel rests on the central spine. As you can see from the photo the aft one is just behind the the saildrive, the middle one is roughly in line with the main bulkhead in front of the engine and the forward on (not shown in the photo is roughly alongside the mast. Note that these supports do not take any significant weight they are there to stop the boat from moving - the weight is on the keel. If the boat is left unattended in the stormy winter months, or people are going to work on it along the deck or inside we also put an additional prop under the bow and two more at the stern. We always take all sails off and lower the spray hood to reduce windage.
Hope this helps