Isn't brace height dependent on the amount of reflex/deflex? Isn't that the reason why most longbows have a low brace height, because they don't have much deflex? And why some recurve bows such as BW, with a lot of deflex, have a high brace height? Wouldn't a BW with a brace height of 8 1/2" have about the same tension on the limbs as a straight-handled longbow with a brace height of 6 1/2"?
That's why I wonder about general rules, such as starting with a brace height of 6 1/2" and tuning up from there. I would imagine that if you started tuning a BW from 6 1/2", you'd probably have to change the string before you got to the correct brace height, whereas if you started some longbows there, you might be starting too high.