The dolphin striker is from the old square rigged sailing ships. It is the vertical spar at the bow at the aft end of the bowsprit. It is part of the structural support to stiffen the bowsprit which supports the forestays from the bowsprit to the mast. In that location it would point down to where the dolphins would swim ahead of the ship. In a Hobie its purpose is to be a structural reinforcement of the crossbar and, in fact, forms a truss. In the Hobie there is a tremendous amount of force involved in the crossbar with the loads from the mast and shrouds.
I once assembled a square rigged model and when I got to the final lines from the bowsprit to the dolphin striker and back to the hull, the whole rigged tightened up. I was surprised at how it all came together and how much each line is important.
Howard