A low brace is just that much closer to your arm due to arm angle so more likely to hit your arm. However, your grip should not place your forearm tight against the string. If there is room between your wrist and the center of the bow you should not hit your arm unless you tork the bow a little on the shot, or your form is off so you shot into your arm. You could have your arm too straight so instead of shooting parallel with you shoulders your are shooting angled into your bow arm because your bow arm is straight, but in line with your shoulder, and your draw arm is out from your shoulders. Look at the form clock. draw your bow shooting into a mirror and check your bow hand, draw arm alignment and make sure they are in line and parallel to your shoulders. If your bow arm is in line or close to inline with your shoulders there is your problem. I had problems with LB's, but no my curve. I made a form change and now I don't use an arm guard with most LB's, but when I shot a low brace LB I due just for insurance. The clearance is so close it is easy to slip up on grip to arm alignment just enough to hit on occasion.