[Jim S]

OB at the 1/2 yard line. The goalline extended ONLY applies to ball carriers who are touching the ground. If you dive it disappears.
WHY? The goalline extended allows a player that is running alog the sideline to protect the ball by keeping it on the outside of his body and still get the ball into the EZ without having to shift the ball. It also allows for a catch where the ball never technically gets in the EZ.
The extension disappearing when a player goes abourne takes away the ability to intentionally "leave" the field and still score a TD.

Now the rule says you put the ball at the spot the ball crossed the sideline.
Play: Ball carrier is running down the sideline and extends his arm (and ball) over the sideline at the 10. (He's keeping the ball away from the defenders.) He dives from the 2 to outside the pylon. Where you going to put the ball?