Ballyclare man Maybin is level par with 16 holes completed at Loch Lomond, having had a birdie and a bogey.
US Open champion Graeme McDowell is one over par after 15 and Belfast's Michael Hoey is three over with one to play.
Maybin birdied the first and ninth, but dropped a shot at the sixth and is four behind leaders Edoardo Molinari of Italy and Graeme Storm from England.
Hoey picked up three birdies on the front nine but suffered a double-bogey seven at the sixth.
Darren Clarke, still chasing a spot in the Open, tees off at 1350 BST.
The former Ryder Cup star needs to have both a top-five finish and be the leading non-exempt player at Loch Lomond to qualify for St Andrews.
McDowell, back on the European Tour three weeks after his US Open victory, has had two birdies and three bogeys.
The Portrush player had said on the eve of the event that he would never get sick of being introduced as the US Open champion.
But, before hitting his opening drive, the official starter opted merely for: "On the tee, from Northern Ireland, Graeme McDowell."
Article from BBC Online
