Tauranga's Oceanna Hardwidge finished fourth overall at Te Kuiti, with Te Awamutu's Chloe Steel rounding out the top five.
Struggling with her fitness, former national champion Elwin had been disappointed that she finished only third overall at the women's nationals near Opunake last month.
"I've not been 100 per cent lately and I will now rest up to let my old shoulder and back injuries heal properly before my next big event, the annual Whakatane Summercross just after Christmas."
Elwin is supported by Motorcycle Central, MX Antix, Ndub Designs, Moss Institute, BikesportNZ.com, Oakley goggles and SFX Seats.