I use the Gutermann thread as well, and the Skala 360 is the same diameter of the 70 denier. It does require a bit more wraps but I don't mind and it makes a really good leader. If I'm not mistaken though the reason John likes the Fly Master thread is because of its properties in comparison to polyester thread. The Fly Master is pre waxed and wont absorb water like the polyester allowing it to stay in the surface film where the polyester if left untreated will absorb water and sink. My leaders float when I apply the floatant to them to allow them to stay on top. This is why I use polyester though as if left untreated it sinks well, and if treated floats just as good. I do have some leaders made from the Fly Master 70, 140, and 210 denier thread. Sportsmans here in Idaho Falls carries the 140 denier John if you would like I can get you some and snail mail it to you. This was atleast last I checked some time last year!