Webb Simpson has stormed into a four-shot lead after the Shriners Hospitals for Children Open second round on Friday, while Australian John Senden remains in contention. The American 2012 US Open champion carded an eight-under 63 at TPC Summerlin to move into 15 under at the PGA Tour event. Simpson leads five players by four shots, including Senden and Americans Jeff Overton, Chesson Hadley, JJ Henry and Jason Bohn. Henry, who carded a stunning 11-under 60 to hold the overnight lead, was unable to replicate his form of Thursday as he produced a 71. In perfect scoring conditions, Simpson took advantage as he holed nine birdies and a bogey at the par-five 16th. “I was wondering why the scores were so low yesterday morning because I thought the ball might go a little shorter,” Simpson said. “But the ball was getting out there and the golf course played a little shorter than I thought it would, and I just putted well and kept going.” Senden (66) went through bogey-free, while a double bogey at the 17th cost Bohn (64) outright second. Hadley (66), Overton (68) and Henry (71) joined Senden and Bohn in equal second heading into the weekend. Defending champion Ryan Moore (63) and Scot Russell Knox (65) are tied for seventh at 10 under. Argentine Andres Romero, who sat second after a 61 in the first round, produced a dreadful 10-over 81 to miss the cut. He combined six bogeys with a double bogey, triple bogey and a birdie. Meanwhile, Australian Greg Chalmers carded a rounded of 68 to be seven under heading into Saturday&aposs third round. Countrymen Stuart Appleby (68) and Geoff Ogilvy (67) are three shots further back.