1.9 should be plenty (strength wise) - it would probably hold me and I weigh about 115 kilos right now. If you don't have evolutionary ties to the walrus like me, you can probably even get away with 1.4 weight nylon.. Almost any light, reasonably strong materiel will do - it's not as complicated as they make it out to be. My speer I always use is sewn out of nylon that is "about that weight" - I paid $10 for the materiel
I use a single bottom most of the time, and do fine in that with a pad in the hammock. I have spent one night in a double which I now own. I like the double with the pad, although the extra weight is a consideration. If weight is not your primary concern you may like the double bottom better to put a pad in, although it's more complicated sewing.