But it could have been even better for the former University of South Alabama star as he bogeyed two of his last four holes at Cordoba Golf Club.
Maybin birdied the second, fifth, 10th and 14th before those late mistakes left him on level par, nine shots behind leader Taco Remkes of the Netherlands.
Remkes holds a two-stroke lead over Argentina's Carlos Cardeza and Estanislao Goya in an event dual-sanctioned by the Tour de las Americas and the Challenge Tour.
Stephen Browne hit a one-under par 70 to share 35th place on one-over par.
But US Open champion Angel Cabrera's 71 dented his chances of winning the title for the fourth year in a row as he slipped to tied 15th on two-under.