Hard shadows on concave surface with positional light v1.7

[brandpeter]

I'm a new user, so I might be doing something wrong, but I just can't seem to get the shadows right on this object where it folds into a concave surface.  I have tried global lights which cast shadows from projections inside the "cave" on its outer rim. Placing a positional light in front of the cave like you see in the parameters L2 doesn't seem to shine any light to counter the shadow cast by the global light L1. Moving the light L2 inside the cave throws the light okay, but does not render a hard shadow.

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