The commanding performance was a welcome confidence boost for the young New Zealand line-up, who earlier in the week had been shown up by their understudies in the New Zealand A side during a training match.
Southby admitted her young charges had exceeded her expectations in their first hit-out.
"I thought we should be able to do it by 10 goals, but to do it the way we did I was really pleased with," she said. "We know it wasn't perfect, but the good thing was they stuck to the structures, kept working together and stayed connected throughout."
With the Ferns holding a healthy 12-goal lead at halftime, Southby got an unexpected opportunity to go to her bench in the second half, introducing Steel defender Jane Watson for her test debut in the third quarter. Shooter Te Paea Selby-Rickit took the court at goal attack mid-way through the final period.
Watson, who was called into the Ferns line-up on Friday as a late injury replacement for star defender Anna Harrison, was not originally included in the wider New Zealand squad.
Already down one of their starting players, the Ferns struck another blow ahead of the opening test, with influential midcourter Grace Rasmussen falling ill on the eve of the match.
Rasmussen, the New Zealand's first-choice wing attack, came down with a fever on the eve of the test. While she had recovered enough to take her place in the match-day 12 today, she was not considered a full game option. That saw Steel midcourter Shannon Francois start at wing attack in place of Rasmussen.
It meant further changes to the Silver Ferns attacking end, which had already undergone significant change with the loss of three shooters from last year's World Cup line-up - Tutaia, Jodi Brown, and Malia Paseka - through injury, retirement or pregnancy.
Southby said she didn't allow the disruptions to deter her side.
"These things happen in sport and you've just got to roll with it," said Southby. "We've been really fortunate that the NZ A programme has been running up [in Auckland] this week, so that's given us the opportunity to bring in Jane, and we had another player waiting in the wings if Grace didn't pull through this morning."
Any concerns over how the new-look attack would fare proved unfounded with the shooting pairing of Bailey Mes and Ameliaranne Ekenasio (nee Wells) playing like a seasoned combination.
Mes produced one of her most dominant performances at international level, netting 40 of her 43 shots at goal, in a player-of-the-match performance.
In the earlier match-up, the Australian Diamonds opened the Netball Quad Series with a predictably dominant 68-43 win over South Africa.
