Eliminate/delete this requirement/rule.

The highest point of the paddle head must not be above the highest part of the wrist (where the wrist joint bends) when it strikes the ball.

Now that the drop serve is legal (and I firmly believe it should remain so), we can see that the drop “slap” serve where the paddle is above the break in the wrist does not make a significant difference in the serve.  Any spin, depth, etc applied by the drop slap serve can be legally duplicated by the volley server.

As an official, it is next to impossible to determine this relationship when it is borderline.  The speed of the wrist snap of the serve is too fast.  In addition to the wrist snap, you need to listen to the contact of the ball on the paddle while watching the wrist position.  The speed of the serving motion at contact makes this call impossible in real time.

As an official last week at the USOpen, I observed several pro and amateur volley serves that were borderline and just one amateur player for whom it was obvious (plus she served above the waist).

I would have required a slow mo frame by frame analysis to confirm a correct call.

Therefore I believe that rule 4.A.4 should be eliminated — as long as the below the waist and upward motion (which can be 0.10 degree below horizontal) should be retained.

All volley serves.