Ah yes, that makes a lot of sense! Thank you for that. The only thing I don't get is this part, "Say tension is right at 9, or 0, but wrong in the middle and opposite ends." If it's right at one end of the spectrum, shouldn't it be right throughout? Let's say it's right at 0 (there's barely any drag on the thread) -- if you then push the ring in and turn the silver knob, won't it then be wrong at 0?