Canadian Brooke Henderson opened a three-stroke lead Friday (Saturday AEST) in a 30-hole day at the Meijer LPGA Classic.
Su Oh finished day two as the best-placed Australian at six-under - 10 shots behind Henderson, who tops the field on 16-under. Oh's compatriot Minjee Lee sits a further two shots behind at four-under. Katherine Kirk is the only other Australian projected to beat the cut, sitting at two-under on the leaderboard.
Trying to break a tie for the Canadian victory record for both women and men, Henderson completed an eight-under 64 in the rain-delayed first round and shot another 64 in the second round at Blythefield Country Club.
Henderson finished play late Thursday (Friday AEST) with a hole-in-one on the 15th hole, her sixth hole of the round that started seven hours late.
"I was able to carry it on early this morning," said Henderson, the 2017 winner at Blythefield.
"Then I had lunch and came right back and played another 18. I just felt really confident today with my ball-striking, which is awesome, and I rolled in a few putts, too."
The 21-year-old Henderson successfully defended her Lotte Championship title in April in Hawaii for her eighth LPGA Tour victory, tying Sandra Post's Canadian record. George Knudson and Mike Weir share the Canadian mark on the PGA Tour, also with eight victories.
Henderson birdied five of the final six holes in the second round to break the tournament 36-hole record she set in 2017 by two strokes.
"With these soft conditions you can take it pretty much right at it, which I've been doing," she said.
"To shoot scores like that you have to have everything kind of working for you and you have to get some breaks along the way, too, which I did.
"I think playing well last night, finishing off with a hole-in-one before going to sleep was really exciting for me, and I was just able to back it up this morning, which is cool."
Brittany Altomare was second at 13-under after rounds of 66 and 65. She played 31 holes Friday (Saturday AEST).
"It was long, but we made the best of it," Altomare said. "I've been struggling this year with my putting, which is normally my strong suit, and today and yesterday, I guess last night into today, it just kind of all clicked."
Jennifer Kupcho shot 67-67 to reach 10-under, playing 29 holes Friday (Saturday AEST). The former Wake Forest star is making her third professional start. She won the inaugural Augusta National Women's Amateur in April and the NCAA individual title last year.
"I've been hitting the ball really well," Kupcho said. "The last couple tournaments I've been struggling with that, so just to hit the ball well has been nice. I hit a lot of greens both rounds. I would just say pretty much everything is going good."
Annie Park was nine-under with a hole left when play was suspended because of darkness. Twenty-eight players were unable to finish.
Angela Stanford (68-68), Megan Khang (70-66), Moriya Jutanugarn (69-67) and Nasa Hataoka (68-68) were eight-under.
Henderson's ace was one of five in the first two rounds, one off the LPGA Tour tournament record set in the 1999 Mercury Titleholders Championship. Mariajo Uribe, Giulia Molinaro and Haru Nomura also aced the 15th in the first round, and Lindy Duncan had one on hole seven in the second round.
Henderson played alongside 2015 winner Lexi Thompson and defending champion So Yeon Ryu the first two days.
"It was a really fun group," Henderson said. "Two amazing players and defending champions, so they know how to play this golf course really well. It was a lot of fun making birdies together and just kind of see how they're doing it."
The Australians projected to miss the cut include Sarah Kemp (E), Hannah Green (two-over) and Robyn Choi (seven-over).