first off... i bought some astro turf today and set it to a reasonable slope w/ h2o and soap... but its still pretty slow. probably worse than snowfence...
now i didnt exactly crunch the numbers but i think buying from this company makes more sense .. read on!!
http://www.polyinn.com.au/index.php?main_page=product_info&products_id=10&zenid=4c9cb6bafe985f019bc8c76248b51933