All three need a good showing this week to earn their way onto the 2008 PGA Tour.
Willis shot a 10-under 62 over the TPC-Summerlin course to reach 130, while Trahan had a 65 and McNeill a 64. Trahan and McNeill played on the TPC-Canyons layout.
This tournament traditionally produces some of the lowest scores of the year on the tour, and Friday was no exception. A dozen players were at 133 or better after 36 holes, and John Daly survived the midway cut by shooting a 63.
Daly moved from a tie for 140th to a tie for 45th.
The large group at 133 included first-round leader Bob May.
Willis is currently ranked 213th on the tour's money list, while Trahan is 126th and McNeill 122nd. Only the top 125 at the end of the season receive an exemption onto the tour next year.