Let me see if I can shed some light on this question. Having ventured outside the 'furled leader literature' last year, I discovered an article that is germane to the question that was published by a couple of Scandinavians on "Zero Twist", in which they discuss the results of their, and others, researches into the the maximum twist that can be applied to a material, metal included, during 'rope laying', or furling. According to them, there is a finite point beyond which two or more strands of a given matertial cannot be twisted (furled) together (Zero Twist Point), without breaking. Based on the type of material being used, the proper amount of tension must be applied during the entire process, and 'pig tailing' does not occur (they do NOT use the term 'pig tailing'). They point out that each material will have it's own 'overage' amount that has to be used to furl (twist) the materials together to a desired length (i.e., our 'standard' 10% overage). Unfortunately, they do not provide information on how to determine this 'overage'. Their paper deals with how they determined, and confirmed, the existence of a "Zero Twist Point".
The inferences I have drawn from this paper are that: 1) proper tension is critical to a maximum twist, and applied from start to finish. (The acient egyptians used special large stones for this purpose, which slid across the furling ground.); 2) that breakage will occur beyond the maximum twist point; 3) that using ancient techniques, pig tailing was unheard of (making it of little or no value to us as furlers); and, 4) once you have determined the "Zero Twist Point" for a given material, the appropriate tension weight, and the 'overage' amount necessary to ultimately the desired length of the finished product, the process is reproducible with great accuracy.
How do we translate this to our furling? Using basic technical info on the material to be used and the number of threads in the terminal tippet end, one can reasonably accureately calculate the amount of weight needed to produce "Zero Twist". Using hanging weights of the appropriate size, and setting an arbitrary 'overage' percentage, one sets about furling a leader to breaking point. One must note how close to the % 'overage' the twist was at breakage to establish the accuracy of this %.
One can 'measure' the breakage point by either the use of a stopwatch (timed), or, as I do, employ a micro-switch, a la Skip Shorb, to measure the actual length at which it breaks. With these parameters, one can, or should be able to, produce consistently twisted leaders, all with maximum twist.
It should be evident that I do resort to the technical/scientific literature for answers to many questions, and not just about furling. I fail to see any real benefit to trying to re-invent the wheel when it already exists.