How to make a CAShapeLayer throw a shadow in iPhone OS 3.0 ?

Question

I'm using a CAShapeLayer with a path. Now I want it to throw a smooth shadow with about 10 units of thickness.

First: Yeah, I could create just 11 CAShapeLayer objects and each time increase the outline of the path by 1 unit with an different color and some more alpha on every iteration. But this way I blow up my memory footprint since the thing is half screen size and this would mean to have 11x a bitmap of half screen size in memory.

So since iPhone OS 3.2 I could probably use those nifty shadow properties on CALayer. But I want to stick to OS 3.0. So what options do I have, other than the nasty one above?