I only know of parabolic and catenary curves. A program is used to determine proper catenary curves and it is automated once you enter fabric panel dimensions. Im sure you've seen this subject on the web, that is how I made my choice.
you will also note that the tarps have had a $10 increase, this is because there are key features that were not included in the past, specifically,
1)a small glove clip at the head of the user for glasses, ditty bag, headlamp, etc..
2)an extra tie-out added to the side for a total of 10
3)using FIRST quality sil, not seconds.
I will add that Ive shopped around and have not seen a solo sil tarp of this quality offering features such as FREE seam sealing, first quality silnylon, at under 8 ounces for this price. Get 'em while theyre hot!