Stickbowman and Pearl Drums nailed it for me. Super dry wood becomes brittle and would fail suddenly rather than compression fracture slowly.
And, while I agree totally that wood will, all by itself, settle in at a certain moisture content, i don't think you can neccisarily completely expect all wood in the same geographical area to be treated the same. what I mean is, say regarding your supplier, maybe he buiys ash from a different source, and it is cut, treated and shipped from somewhere else, and you are buying it before it really has a chance to settle in. Or maybe his source uses a hotter kiln and dries their ash faster, and so damages it,. Or maybe he keeps it in a different shed which is just slightly warmer, or gets more wind, and thus adjusts faster. Or, something. And since board bows are often bught and then made right away, ....... who knows.
Ash is NOT, despite it's hardness and numbers, as "good" a bow wood as woods of similar weights, I agree; like harder maple, white mulberry, and heavier elms. But it isn't TOO bad. Think wide and long, trap the back, toast the belly, etc.. and I bet you can do it.
