I' ve seen pictures of guys that have their arm so bent they look like they' re resting their elbows on their hip bones.[

] I' ve seen pics of other guys that have their arm locked out and their elbow is bent THE OTHER WAY! [

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If you shoot low wrist, like most folks recommend these days, rotate your elbow so the inside bend is perpendicular to the ground and the bow hand is setting at about a 45 degree angle from the bow grip, then your arm will naturally take the correct amount of bend FOR YOU. Then it' s up to you to buy a bow with a brace height that matches your natural shooting form.
I do not believe in creating an artificial bend in the bow arm (like most of the guys shooting ultra low brace bows must do). For one reason... It' s practically impossible to create exactly the same bend on each and every shot.