Nigel,
These clips should have two tips (back face) one is solid and the second is on the bendable tab, these goes inside the opening on the rocket panel. The drawing on page 137 of RSS catalog shows these tips. It will be best to bend this tab just enough allowing the clip to go in with light pressure, once inside you could use a small flat head screwdriver to bend the tab slightly and secured it in place.
If you some pictures, just shoot me a PM..!
Good luck..!