ironraven The kind of mason's twine I was refering to and see most often is nylon not cotton. The packages I have on hand are rated at 175 pounds. It is roughly twice the thickness of the inner cords of 550.

I can see breaking 550 as a support line but as the mesh. The multiplicity of the lines in a mesh hammock would easily support more weight than would be ever needed.

I think the cotton twine you refer to is what most commercial hammocks are usually made of.