The best possible sheeting line I have ever seen just came on the market last year from New England. Is is called Salsa and comes in 1/4" 5/16" and 3/8" and in two colors, red and green.

This is the best sheet I have ever used.., it does not absorb water, easy on the hands, goes through blocks very well, does not stretch, does not kink or knot while laying on the deck.
It does not have a core, yet doesn't stretch. Check it out.
http://store.catsailor.com/tek9.asp?pg=products&specific=jnqmmmgqg8
http://store.catsailor.com/tek9.asp?pg=products&specific=jnqmmqmml0
http://store.catsailor.com/tek9.asp?pg=products&specific=jnqmnonpe0
And the price is very reasonable.
Hard to beat this stuff.
Rick