An Aluminium 0.02" backing plate was added to give more strength and the Alternate Air Flap or Bypass Flap was manufactured with a backing rubber seal; using silicone was too frightening particularly with unpainted parts around. The basic idea comes from the Glasair III induction box flap. The two springs will have locking wire passed through them and silicone put on the springs to ensure any broken spring is not sucked into the engine. Tabs were added with #6 screw Clickbonds to enable to structure to be screwed together rather than riveted which makes it impossible to check the Air Filter.
