Carrera Rear Reflector - What's the trick for these clips?

[Crachian]

There has got to be a trick to installing these way-too-complicated spring steel clips. The inner piece that clamps the plastic "screw" has two tangs that hold the entire assembly to the car, but after spending 45 minutes getting the first one in (and I still don't think the second tang is sprung out all the way), I'm thinking there's got to be a trick.