A few years back I experimented with a plain siliconized nylon 8'x10' tarp. The tarp itself worked fine even on a rainy night. Where it did not work fine was in the company of mossies, where I had a miserable night. I solved the mossies problem with netting but realized I was defeating the purpose of saving weight. Especially these days where tents are available weighing little more than a tarp and bug netting.

When unable to call upon a reserve of experience in sleeping out, the suggestion from above to doing a test run in a back yard or nearby campground is good. Leave yourself a way out.