An excellent guide to setting up a tarp - including use of a ridgeline - can be found by going to http://www.cookcustomsewing.com , clicking on the Explore CCS link, clicking on the Tundra Tarps link, and then scrolling all the way too the bottom of the page and clicking on the Tundra Tarp Setup link.

The Tundra Tarp by CCS is my own favorite multi-use tarp.

I've used those plastic tarps enough to know that I can't rely on them - they tend to rip and the grommets tend to pull out during storms - when they're needed the most. They are also heavier and harder to pack than their nylon counterparts.

Ken