Ellis, Arca's thumbscrew adjustments only set a lower limit on ball tension; they don't restrict how hard one can crank down on the main knobs. If you're referring to rotation of the number scales, yes, I am aware that they should be set to match the camera load attached. However, no matter how hard I hand-tightened main knobs, neither head could resist leverage of a physically large camera as described above. Perhaps using a pair of pliers on the knobs would have generated enough force, but that's not something I was willing to try.
I believe this is simply a matter of ball diameter. I find Arca superb for 4x5 and smaller, and still use a B1 in those situations. The 8x10 would likely have been handled perfectly by an Arca B1G with its larger ball, but I was attracted by the Burzynski's lower weight and method of attachment to my Gitzo's yoke.
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