Chua and Roberto, who scored 51 points apiece in the first round, tallied 52 points each this time but De Guzman did better with 53, making it a three-cornered fight for the championship in the oldest lady golf event now celebrating its Ruby Anniversary.
Chua and Roberto both had a two-day aggregate of 103 points under the Stableford Scoring System. De Guzman was two points behind at 101 while Carmellete Villaroman was at 96 after 49 points.
The 26-year-old Chua, the winner in 2000 and 2001, survived a fat 40 in the front nine for a two-over-par 74 in a wooly second round that also saw Roberto fire a 74 after going through a roller-coaster trip.
Chua birdied three holes coming home, including the last hole for her 34 while Roberto finished birdie-birdie to offset a double bogey on 10 for a 37-37 effort.
The 32-year-old De Guzman rallied with a 73 for 53 after a mediocre 77 (48) in the first round.
Rounding up the Championship Division cast are Eva Miñoza of Del Monte 47-48-95, Lucy Landicho of Canlubang 48-46-94, Tracy Locsin of Southwoods 44-49-93, Stephanie Yu of Wack Wack 43-40-83, Hye Jung Kim of Del Monte 37-41-78.