Seigi,

The reason for using a separate ridgeline is support and easing of tenion on the tarp at that point. My tarp (MLD poncho) has a seam down the middle so I don't need it, but have used it before I had this tarp.

My method of determining guy line lengths was simple. I set up the tarp using cheap butcher's twine and then measured the pieces.

I use several different pitches depending on terrain and weather, so I carry quite a few different lengths (I think I have ten). I have a very light, very strong cord from MLD, so the extra weight is not a problem.

I also use very small light biners and tensioners, also from MLD, to make setup very quick and easy. I use my hiking poles whatever the pith unless I find handy trees or branches.

Hope that helps, best, jcp