I am interested in the claimed very high strength fluoro-coated nylon lines such as Konger, which claims the 7X (0.12mm) has a breaking strain of 5.5lb. I tested this with a pull test by tying line to a pull balance with a clinch knot. It broke just above the knot at 4.5lb, which isn't bad considering what strength you would expect to lose with the knot. But is this the best way to test for breaking strain? It is essentially what Yellowstone use in their pull test. It seems to me that it would relate to the fairly constant pull you get when playing a fish, the sudden stress of the lunges being taken up by the flex of the rod, the drag and the skill of the angler. Others, though, tie the line to a rigid bar and drop a weight. This seems to me to be more of a shock test than a breaking strain measure? Even when retrieving lures with a straight rod, there is always some give in the fly line, the leader and how you are holding the line to reduce the shock. Not surprisingly, lines that have little stretch, such as fluorocarbon or pre-stretched nylon do not come out well in that test - but does it represent anything the line would encounter in use? Would you get a different result if the line were tied to a bar with a give in it to reduce the shock impact?