Negrido, son of a teaching pro at Villamor, completed 36 holes at the up-and-down Tat Filipinas course at 145 after his opening-round 71 with Dimabuyo behind him at 154 after a 76.
In Class B, Gino Bunyi was leading the boys division.
Over at the Riviera Executive course, victory was again in the bag for Wolen Juan Superal in Class D.
After his streak of under-par rounds ended on Monday, Wolen had a 54 to increase his lead to 15 over James Christian Ricohermoso and was a cinch to pick up his ninth straight win.
The 54-hole tourney is also given major backing by Philippine Airlines, Airlift Asia, Air Liquide Phils., Global Lighting and Exito Manufacturing Bellevue Manila. Third World Eximport, HBW Ent., MCCI Corp. and BF Technology are minor sponsors of the tour.
The Class E division leaders were JR Gonzales and Sun Mi Hung.