Cowper confirmed he is likely to do the whole series, given they were not necessarily going to compete on Sunday if their new truck was not going to be ready in time.
"I guess [we will]. That's the best possible start.
"It's also good to let some young blood come through, but you don't want to give it to them on a silver platter."
Auckland's Scott Briggs, last year's runner-up in the championship, was second to Cowper with 459.7, while Wanganui's defending NZ1 Hamish Auret finished third with 518.6.
In the C Class, Wanganui's 4WD club president Paul Chapman acted as co-driver Phil Conwell, known as the 'Fireman', and they won their group while coming third overall with 494 points.
Locals followed in second and third in C Class, with Kevin Hermansen and Kirk Grant coming runner-up, while the father-daughter team of Grant and Renee Harrison were third.
On the day, the Harrison's were really enjoying the challenges, as the wet weather of Saturday had dissipated in the heat of a cloudless morning.
"It'll dry it out a bit for the afternoon," said Grant Harrison.
"I thought it'd be a hard day, but give it a go and you go all right."
The team had just completed the muddy bluff hazards at the left end of the course, closest to the public carpark.
"It's good, technical stuff," Renee explained.
"It makes you think," Grant added.
"There's some cautious guys, and then there's some guys that have a go at anything. Hard nuts."
Auret could testify to needing momentum, as by the time he and co-driver Paul Barnes went up course No29 the mud was so deep that they buried one of the points markers.
"That one's gotten deeper and deeper as it goes. Not much we can do about it," he said.
While there were also spectacular spills and thrills as the trucks tried to navigate up sheer vertical heights or through boggy terrain, one the more eye-catching moments was the fate of South Waikato's Steve Morley and Kevin Morley.
The Morley's rolled their F Class truck sideways down a small a hill, adjacent to where two other trucks were parked while waiting to undertake the neighbouring course.
"I saw that. I was a bit worried for a minute, thought he was going to roll into it," said Cowper.
There were no injuries as the Morley's turned over three times and landed perfectly in line behind the other trucks.
