I can't find the right link to the original thread on this system, so here's how it works.
You look at the halftime score compared to the original line and determine what the 2H line should be based on that number.
Example: Georgia vs. Florida, Line is UF -10. If Georgia is leading 7-0 at halftime, then to cover the original line, the 2H line should be UF -17.
Then, you see what the actual posted line is, and figure out what the middle is.
Continuing the example: If the real 2H line is Florida -7, the middle is 10 points. If the 2H line is Georgia -7, the middle is 24.
The original system called for a play if the middle was 10 or more points. Usakangy tighted it last year with some success as follows:
If middle is 10-14.5 and play-on team is road favorite only, play it
If middle is 15-20.5 and play-on team is road team or a favorite, play it.
If middle is 21+ play on any team.
If the middle hits the specified range, you choose the play-on team based on the team that has created the "good" side of the middle.
Continuing the example: If the 2H line is Florida -7, the middle is only 10, which doesn't hit the tightened criteria, so no-play. If the 2H line is Georgia -7, the middle is 24, causing a play to hit. The play would be Georgia -7
This system did well in the early season last year, and tightened up as the year wore on. Hopefully it'll look good early this year, too!