The shape of the keel on a Seastream makes the boat particularly suitable for beaching legs. In fact the boat will stand upright on its own on a flat surface! Once, when I was having the boat lifted, I asked the crane operator to lower the boat onto its keel and slowly let the straps go slack. The boat sat perfectly upright on its own!
Below is a photo of Shadowfax dried out on Bell Isle in France. The legs are from a company called Yacht Legs and they attach at the beam with a quick release socket. They can be assembled and attached in approximately five minutes. They are set as default to the depth of the keel but initially I wind them up using a small handle on the top by a few inches. Then when I know the keel has touched down I will wind them down to also touch the bottom.
There is very little weight on the actual legs and they purely keep the boat upright. All the weight is on the actual keel of the boat. In this position, once the legs are set, you can rise and fall with the tide quite happily. Needless to say you need to do this in a sheltered anchorage or harbour where there is little or no swell.