Every launching situation will have it's own issues. Narrow channel, boats... this is a generic description.
You can start with one down or partly down. Be a bit easy on the main sheet as that forces you to round up. Start with the boat at 45 degrees or more off the wind. As soon as you hop on, the boat starts to round up. Steer with the windward rudder partly down. From your sailing position you can be pressing down on the tiller arm. As it get deeper, you can be pushing the rudder down further. When in deep enough water, round down a bit and fully sheet out. That way you are not going to round up head-to-wind as you lower the rudders. Then drop both rudders and off you go.
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Hobie Cat USA