Have you 'tarp Aficionados" thought about using a braid fishing line?
Take three lengths of - say - 150lb strength- and braid it. Thin, light, strong. 450 lb.
And the braiding will give it bit of stretchiness.
Nope, fishing line is too thin and fiddly for me - in the cold and dark I need a line I can see and handle easily - as bright as possible and as thick as is sensible to minimise tangling.