Gilliane, I do know that one or two Christchurch members have made simple slide up and down plates to get them in and out of that shallow harbour.
But while we were at the Beaulieu 'do' for Parkers 25th we saw a clever version for shallow draft steering on Black Jack (SS no 4)
Paul had made a simple aluminium lifting plate that was bolted alongside the normal stock that could be lifted and lowered independently in the same manner as the main rudder. The draft was organised to be just below the propshaft, when swung down, to give full propwash control...though a little to one side. He demonstrated the efficiency of this, with his main rudder fully lifted, on the way out of the river. I did take the measurements but currently can't find them so if you manage to get them please pass them on!
Paul Morris is in the book.
Chris.
Chris Turner