Erc is tension weak wood and likely to break even without knots on the back of it, your stave has huge knots making it a great candidate for an even more sudden explosion. I am a carpenter and have worked with tons of erc building cabinets, flooring, and chests but I have never made a bow from it so take my 2 cents for what its worth. Btw, Im pretty sure that bow you posted the link to broke not long after Ryan posted it. Maybe Ryan will chime in about it. Not trying to be discouraging to ya but If you are really wanting to make a bow from erc then I would try to find a cleaner piece than the one you have.