It's a truly international-calibre class with both the Australian riders having represented their country at the big annual Motocross of Nations - the Olympic Games of motocross - in Europe and Cooper, Columb and Groombridge, among others of the Kiwis, have each in the past flown the Silver Fern flag for New Zealand at the same event.
That international experience could be vitally important in Rotorua this weekend.
Ferris and Waters have never raced at the Rotorua track, while Cooper, Columb and Groombridge have an affinity for the place and this could change the dynamics on race day, although both Ferris and Waters have so far proven to be fast learners.
The MX2 (250cc) class seems to belong to Harwood this season. In the six races over the two rounds thus far, the 20-year-old Harwood has won three of them and finished no worse than third in the others.
Harwood will be nervously looking over his shoulder as the man giving him chase is another Australian first-time visitor to New Zealand this season, Victorian Jed Beaton, just 17 points adrift, while Reporoa's Hadleigh Knight, Waitakere's Ethan Martens and Rangiora's Micah McGoldrick make up the top-five list of MX2 class contenders.
Knight will regard the Rotorua track as "home turf" and could be expected to mount a stern challenge this weekend.
"My campaign this year has been going way better than last year, but I'm still disappointed with what happened at round two of the series in the Manawatu (just over a week ago)," said the 19-year-old farm worker.
Knight had been second and just six points behind Harwood at the start of the day in the Manawatu, but finished a lacklustre sixth in the class that day, slipping back to third in the standings and now a massive 35 points behind Harwood.
"I'm looking forward to Rotorua ... and the final round at Taupo too. Those are my favourite tracks and I usually go well there. I know both tracks like the back of my hand."
In the 125cc class, Thames Valley rider Broad enjoys having the biggest margin of any of the class leaders.
He is 28 points clear of his nearest challenger, Taupo's Wyatt Chase, but Broad is also aware that with 25 points on offer for each of the remaining races in the series, he can't afford to relax and something even as minor as a flat tyre, a crimped fuel line or broken spokes, or a worse than that, a crash, and his lead would quickly evaporate.
Feilding's Tony Cvitanovich, Karaka's Kurtis Lilly and Beachlands' rider Blake Gillard are also on the pace to claim a podium position for themselves in this class.
There is little break for the riders after this weekend, with the fourth and final round set for the Digger McEwen Motocross Park facility, on the outskirts of Taupo, just one week later, on March 20.
