Lee opened with a bogey on his first hole in Round Two, but then turned on the birdie machine.
He ripped off four in a row, starting at the second hole, and hasn't looked back.
"I just got comfortable," he said of his turnaround.
"I hit it better and I putted it better. Somehow, every time I hit it on the green, I can read the greens really nicely.
"I don't know if it's the green colour or it's Midland, or I'm just having a good time."
Lee is having a blast, because he's making everything he sees.
He leads the field in putting and has chalked up a tournament-best 23 birdies thus far.
"It's similar to the Four Seasons, where I practise," said Lee, who moved to the Dallas area last year and plays at the TPC Las Colinas.
"I can read the putts really well."
Thanks in part to a playoff win last year, Lee finished sixth on the Web.com Tour money list and earned playing status for the PGA Tour this year.
His rookie season hasn't been overly impressive and he has had to sit out the FedEx Cup playoffs, which are concluding in Atlanta this weekend.
In an effort to sharpen his game, Lee has made a couple starts on the Web.com Tour in preparation for the PGA Tour's Fall Series.
"Every time I come to the Tour, it feels like I'm getting my confidence back," he said.
"I know what's wrong - I'm working on that and starting to play better."
Percy will join Lee in the final twosome, provided he can catch his breath.
The 38-year-old has been battling asthma this week and finds himself short of breath quite a bit.
"I've really been struggling," he said in a hushed voice after his day.
"It's hard to speak when your heart is racing."
Meantime fellow Kiwi Tim Wilkinson, who is currently 59th on the Web.com money list, has carded rounds of 67, 71 and 71 to be in a share of 16th place and nine shots back from Lee.
Hamilton professional Steven Alker fired scores of 70, 71 and 73 to be in a share of 53rd place.