I have repaired at least 8 Hobie 18s and 18Ms in our fleet that had cracks under both front and rear crossbars and shroud connectors. Some cracks were a foot long and the hull had not broken off yet, amazingly. But they WILL BREAK if not repaired. Some of these had been older boats- pre'85 without the reinforcing D-plates. Magnums often split under the left front and right rear crossbar, sometimes at the inside lip but usually the outside lip. The wings add too much stress that the boat was not designed for. Turn them over and add epoxy/ fiberglass inside, even in front of the crossbar, as far as you can reach.

Signed, Catcobbler