I once saw a coach who wanted his players to be in "perfect position" when attempting to do basic smashes or clears. He would pop up high shots and then make his players get into position by allowing the birdie to hit them right on the forehead without even holding rackets. they were wearing what looked like hockey style plastic visors, but I thought that was really unique. the idea was to create that perfect straight line i think when attempting these shots, as opposed to "reaching" or "stretching" for these shots, which is not ideal. I've also seen a doubles team being trained by having 4 people on the other side. although i think this is relatively common. what have you guys seen?