[nvfoa15]

2-16-2g The enforcement procedure for a foul by the receiving team during a scrimmage kick has been changed. The change reflects that should a foul occur by the receiving team on its side of the expanded neutral zone prior to the end of the kick, the receiving team shall retain possession of the ball following enforcement of the penalty. The foul does not apply to a try.

Mike,

This is the wording I found on the NF web site. Although this statement is not very explantitive (my opinion), I believe that you can derive several requirements for PSK enforcement:
1. a scrimmage kick that crosses the LOS.
2. the spot of the foul by R is beyond the expanded NZ.
3. R's foul is before the kick has ended (loose ball).
4. R must have possession of the ball when the down is
over (if K possesses moot point).

The NF web site does not give a revision of the penalty enforcement rules with regard to PSK. However, under NCAA rules (I think), the spot of the foul and the spot where the kick ends are important. The enforcement spot is the end of the kick unless the foul is behind this spot, then enforce from the spot of the foul ("hit'em where it hurts the most!"). For touchbacks (an unsuccessful FG could be this) the end of the kick is the 20 yard line, thus it is used for reference point for penalty enforcement of PSK.

If I'm far off I'm sure somebody out there will correct me.