"We're more than happy, I've never been so happy to come fourth," Cowper said.
"We pretty much for 90 per cent of the morning were mint, but there was two courses in a row [with bad scores].
"One was an uphill bog, people were getting stuck in the middle of it."
Cowper and Hermansen then decided to try and take an outside line on their climb up, but one of their wheels nicked a yellow flag marker on the course boundary, leaving them with 90 penalty points.
"We were only 20mm offline," Cowper said.
"The next one came down across the ditch, had a double to climb. We flipped over backwards, right on our roof."
That added a further 80 penalty points to the tally and the experienced Cowper figured the day was now a writeoff, despite the fact the truck itself was running flawlessly after dropping the transmission out and replacing an oil seal on Friday.
"For us, they [should have been] zero's, so that was just bad luck."
But despite handicapping themselves with 170 points they didn't need, Cowper said they did not give up hope because from 16th spot up to 8th was a spread of only 100 points after the morning session, so a strong afternoon could salvage at least a Top 10 finish.
They proceeded to deliver by completing 12 of the afternoon obstacles with no faults, while conceeding only 20 and 40 points on the last two obstacles.
The team did give up 80 points on the very difficult 16th obstacle, but all the other drivers did the same or worse.
"We won the afternoon quite well and surprised everyone," said Cowper.
"We were able to leapfrog all those guys, sort of unheard of a bit."
Getting a Top 5 could prove crucial later in the season, as after the six rounds the drivers drop their worse result from their final tally, so Cowper may still need this number or could possibly discard it if he makes the podium regularly.
"The truck's actually on the market, I want to build a new one, but at this stage we're doing the full season."
Auckland's defending national champion Scott Biggs, who claimed the title by only a point last season from Whanganui's Hamish Auret, won the Wellington round with a very tidy 343.01 penalty points, comfortably ahead of runnerup Derek Smyth of Manawatu with 469.02.
Waikato 4WD vice president Neville Mather was only 2.29 points further back in third, while Waikato's Greg McDell rounded out the Top 5.
Cowper took note that the Top 3 drivers were all in Nitro Customs trucks, which are built by the Biggs brothers, Scott and Jarred.
The Turakina truck-builder is hoping to see more of his clients do better as the season progresses.
The next round is being hosted by the Manawatu 4WD club on December 1, which is where Auret has targeted to make his comeback as he completes recovery from the broken leg his suffered on his farm in mid-October.