She stormed to victory on Saturday in the women's races, leading her rivals home by well over a minute on each of the three outings.
Not even fellow Yamaha ace and national women's champion Sarah Elwin, of Taihape, had an answer to Duncan's blistering pace, finishing runner-up each time.
After being sidelined for much of 2013, following a concussion while racing in the United States that year, Duncan (18) showed she was back to her scintillating best and keen to mix it with the boys in the national 125cc class on Sunday.
She qualified her Yamaha YZ125 in the No 1 position and finished 1-3-4-1 in her four races.
Riding her much smaller and less powerful 125cc machine she then managed a 19th placing against the 250cc and 450cc men in the all-in feature, giving her the outright 125cc class win ahead of Onewhero's Jayden Turnwald.
''It was certainly a good way to start the season off,'' Duncan said.
''But there is always room for improvement. My starts let me down and I know I can't afford to start way back in the pack and expect to come through. My pace is good, though, and I expect to be better the next time I race.''
Duncan's competition schedule includes the Southern Series, where she will race the MX2 (250cc) boys - ''just to give me tougher competition''.
She will race the national 125cc class at the Auckland championships on December 6-7 and then plans to tackle all rounds of the national championships.
The weekend's MX Fest was her first major shakedown before the national series, which starts near New Plymouth in February.
Queenstown rider Scott Columb flew in from Europe two days before the Taupo event to tackle many of New Zealand's leading 450cc exponents in the MX1 class.
Columb finished no lower than fourth all day and easily earned the third podium position, behind Taupo's Brad Groombridge and Warkworth rider Hamish Dobbyn.
''There were a lot of races today and I hadn't been on a bike at all these past few weeks,'' Columb said.
''To finish on the podium was the aim and now I will be building up towards the nationals early next year.''
Dunedin riders also featured.
Campbell King was fifth overall in the MX 2 category, while Grason Veitch was sixth overall in the junior 12-16 years 85cc class.
