Al, Thanks for the clarification from DrJ's writing. I'm not sure that I agree totally with him entirely on the all (some, yes) of the points he makes of the single guyline benefit. His other theory in the article seems very sound, showing much more understanding of the subject than I possess. However, in all but one case, when I've "nitpicked" with him via email over some minor technical/engineering issue, I've been wrong and DrJ's been right. Probably if we analyzed his approach mathematcially (e.g. a vector analysis of the loading of the tieouts and tarp using both guylilne methods), I'd be wrong again, but just visualizing what is actually happening if a rectangular flat tarp has 'V'-shaped webbing tieouts, I'm not sure that there would be too much difference in panel loading (not guyline and stake loading, which is improved) between the single guyline per tieout and the single continuous guyline. But, that's just an off the top of my head, close my eyes and visualize the panel loading analysis. I'm probably missing some key point, that DrJ understands. Of course, I'm visualizing a static loading, perhaps with dynamic movement/shifting under heavy winds, the single guyline starts to make a real difference in pulling on the tarp from different angles as the tarp attempts to shift in response to the wind - that might be the secret. Maybe, the tarp in question does not have sufficiently wide 'V'-shaped tieouts to simulate the pull that the single continuous guyline attempts to achieve? I believe that the primary determining factor in panel loading on the tarp will be how many tieouts are available for use and not primarily the guyline configuration used. Again, stake and guyline loading can be quite a bit different from the panel loading, hence one benefit of the single continuous guyline.
That single continuous guyline per side approach is nice in one sense that if you wanted to use the JrB's self-tensioners, you'd only really need one per side (or two if wanted more "give" in very windy conditions). Two self-tensioners per side and the extra stake required for the continuous guyline approach might make a stake pulling free far less likely and make the whole system far more resistant to experiencing its inherent single point of failure (per side).
I'll have to go take a look again (it's been prob. 18mos) at the article you mentioned. Thanks for taking the time to post back and give me something more to think about - I do appreciate it.