Downes collected four birdies and a pair of bogeys and had a chance to be alone in first until carding one of his two bogeys on his final hole of the day to drop to 7-under.
Patterson, the first-round co-leader, started off with a bogey at the par-4 1st and could only muster 1-under 71. He rebounded with four birdies on his scorecard, yet added another couple of bogies.
The other overnight leader and another Aussie, Craig Jones, closed with a even-par 72 and stands at 6-under through two rounds and is in a share for third with New Zealander Gareth Paddison.
Paddison, the low Kiwi, fired his second straight 3-under-par 69. An eagle at the par-4 3rd and late birdie has him one stroke ahead of fellow countrymen David Smail, Mahal Pearce and Aussie Brendan Jones, all at 5-under for the tounament.
All three posted the same score for the second day in a row - 69s on Thursday and trio of 70s during round two.
Smail, the defending champion, endured a triple bogey early in his round but righted the ship for his 2-under 70.
Grant Waite, the 1992 champion, is in a tie for eighth with amateur Brad Heaven, a local boy who attends the University of Toledo in the United States. The two sit just three off the pace at 4-under par.
Michael Campbell struggled with his putter most of the day, missing several par saving putts inside ten feet, and stands at minus-2 with six players after 36 holes.