Yes, more layers are better, as is a larger area.
But how do you make it work with the pressure plates? don't they get washed away with the water?
And as Sor says, you have to be a bit away from it. I think 20 ish blocks or something (which works in any direction, up, down, sideways, essentially a sphere centered on you with 20 block radius).
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Last edited by DaedalusAlpha; 4th February 2013 at 02:15 AM.