Mallinger carded six birdies against only one bogey to emulate his first-round total of 11 points under the modified Stableford scoring system.
And he was soon joined at the summit by fellow American Henry, who scored 12 points to add to his opening 10 after a round featuring five birdies and an eagle but also three dropped shots.
Matt Bettencourt was two points behind the leaders after also scoring 12 today.
JB Holmes followed a one-point first round by reaching 17 for today through 16 holes, with nine birdies and a bogey.
An eagle, two birdies, one bogey and a double gave Ricky Barnes five points for a total of 16 where he was joined by South Korea’s Noh Seung-yul, who scored three points after an eagle, a double-bogey, two birdies and three bogeys.
Two veteran Americans were in the hunt, with John Daly on five points through 16 holes after scoring 10 yesterday and David Duval finishing on 14 after scoring eight for his round. Pádraig Harrington matched Duval’s two-round total after scoring seven for the second successive day.