#18 braided nylon construction line from home depot. about 1.5mm, and comes in neon yellow for visibility.(dark green too). it's incredibly cheap, light, and plenty strong.
it is a little stretchy, so tarp tensioners are not as necessary as with no stretch lines such as spectra.
Picked up some from Home Depot.....500' for $10.00
Neon yellow. Thanks for the idea.