If you are looking for a way to widen the arc in your backswing, work at the range on pushing the club away from you as you swing back.

Once your club reaches parallel, your right arm is going to break down. What you should be looking for a the top is the bicep/tricep is at 90* to your side, your forearm is 90* to your bicep/tricep and your hand is 90* to your forearm.