>>76517242 (OP)
you're supposed to step out so the cable is pulling your arms directly back rather than down. That gives a much better stretch. It's nice because it's one of the few bicep curls that stretches out the muscle without obliterating the tendons (like preacher curls). Still, doing curls on a double stack is giga-dyel behavior, incline db curls are basically the same movement but respectable