In a day when majority of the field fumbled with fat scores at the hazard-laden, Robert Trent Jones II-designed layout, the 55-year-old Gaston stayed focused and played a steady game to pool a 36-hole aggregate of 150 and seize control in the 54-hole championship staged by the National Golf Association of the Philippines.
The diminutive but talented club bet, who ruled the national amateurs in 1978, had five bogeys but birdied Nos. 7 and 14 for nines of 38-37.
Coscolluela, whose opening round of 74 sparked hopes for a second crown in four years for the Alabang Golf Club bet, limped home with a 78, his bid ruined by an early run of bogeys four and marred by a double-bogey mishap on No. 3. He had nines of 42-36 and slid to second at 152.
Club manager Clifford Celdran failed to cash in on his familiarity with the par-72, all-weather championship course and likewise struggled in the early going with a 40 although he held on to save a round of 77 for 153, three strokes adrift.
Worse was Iggy Clavecilla, who shot himself in the foot with an 82 (39-43) and virtually kissed his title-retention bid goodbye with a 160 for joint eighth heading into the final round of the event backed by Philippine Airlines, Rowell Golf Club, Rowell Group, WWW Express, Nike golf through Pacsports, Bayer Phils. Levitra and Electrobus Callaway golf.
Clavecilla, who rallied with a 72 to snatch last years crown from Richie Garcia, had five bogeys, a pair of double bogeys and a triple-bogey on No. 11 with only two birdies to show.
Bing Bunye of Cangolf stayed in fourth with a 157 after an 80 while Rivieras Danny Pizarro skied with an 81 for a 158.
Bernard Castillo of MSU shot the days best score of 74 but hardly moved up to sixth place with a 160 in a tie with Rolly Uy (78) and Clavecilla.
Meanwhile, Anthony Sasin paced the Category II division (60-64-years-old) with a 79 for a two-shot lead over Reny Go; Ben Trinidad shot a 77 to erect a 13-stroke lead over Romy Garcia (90) in Category III (65-69); Godofredo Galindez made an 84 for a 12-shot lead over Telesforo Takvo in the Super Senior (70-74); while Enrique Beech of the Philippine Sports Commission led the Super Senior II group (75-above) with a 94, 10 strokes up on Frisco San Juan of Wack Wack.