STROKE Render Effect Problem!

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I tryed animate a lines from stroke.
The lines must be growing and moving thru the stroke shapes.
I create a stroke by render effect - STROKE.
Only by this way I can easy control and animate a way of growing lines...
How change the end of this stroke because After Effect make by default a round finish and i can't change this???...
How do it?
I dont want make this by Vector Paint AE Effect because is not precisious and editable...
Maybe there is another effect or solution for this finish of "rounded" stroke.

The example what I wont is on:

http://www.schwartz-fx.com/stroke/

there is a JPG with example ...

Please help!!!