as i recall, impeeding is an ifk; holding is a dfk. if the ball is within playing distance and the defender utilizes arms, legs to keep the attacker at bay, award the ifk. if the ball is not within playing distance, you have a hold. therefore, if done near perfectly but just crossing the line to get an impeeding call, ifk, not a gk. playing distance is the cr's judgement, not a fixed distance. for skilled players it might be 3-4 yards. nothing prevents the attacker from running around the defender to get to the other side. just a time/distance issue. use of the arms, legs to shield is a judgement issue. no one plays with their arms clamped tightly to their side. i believe experienced refs make sound judgements on just how much extension/use is allowed. and, as been mentioned before, the attacker in this situation can legally charge the defender from behind - up to a point - another judgement call. this seems to be a solution in search of a problem. football is played with a simple set of rules that have required relatively few modifications over the years. i would like to see it kept that way.