Final Result: 4-2, +1.03pts 

Before round 1: 

LAY Phil Mickelson to lose 20pts @7.8  (i.e. stake 2.94pts)
LAY Justin Leonard to lose 20pts @24  (i.e. stake 0.87pts)
LAY Charles Howell to lose 20pts @60  (i.e. stake 0.34pts)
LAY Trevor Immelman to lose 20pts @80  (i.e. stake 0.25pts)

After round 3:

BACK Justin Leonard to win 19pts @17.5  (i.e. stake 1.15pts)
BACK Phil Mickelson to win 16pts @8.2  (i.e. stake 2.22pts)

Closing out the play on Leonard, and partially on Mickelson - who I still think is opposable at these odds, so leaving some of the lay running on him.

This leaves the overall situation as:

The field: +1.03pts

Mickelson: - 3.69pts

Leonard: +0.31pts