Matheson, former Hawke's Bay rider Emily Fraser (Feilding), who won gold at the Youth Olympics in China this year, Olivia Robertson (Christchurch) and Melanie Weal (Te Awamutu) are offering two horses each but will not be able to saddle their mounts.
The Aussies will also draw from the collective pool of borrowed mounts.
Robertson is the daughter of former All Black first five-eighth Duncan Robertson, of Christchurch.
Queenslander Gemma Creighton, who has competed in New Zealand on numerous occasions, leads the visitors' charge with Mykaela Briggs (Tasmania), Zoe Boulton (Victoria) and Sophie Ahmat (Western Australia) in the test.
Matheson is offering a mare, Outward Bound, which belongs to Jenny McKay, of Putorino, about 45 minutes out of Hastings.
The other offering, Bellwood Casanova, comes courtesy of Jill Morrison, of Cambridge. The gelding is based at the showjumping yard of Sean Cubbit in Cambridge.
"I've been riding Outward Bound all of last week," says Matheson from Arena on Ormond, a showjumping facility at Twyford.
The riders will have a feel of a fresh mount each day for five minutes before jumping a couple of rounds on them.
The championship overall has drawn elite riders such as Katie Laurie (nee McVean, Cambridge), Maurice Beatson (Dannevirke), Bridget Hansen (Hastings) and Helen McNaught (Taupo) in a field of 180 equestrians involving more than 300 horses.
Hansen says in designing the course he has had to factor in pedigree European sports horses, including stallions from the age of 4 to 7-year-olds.
"I've kept it simple for the 4-year-olds with big loops and not so technical, to close to grand prix level for the 7-year-olds," says the director of the annual Horse of the Year Show in Hastings.
"It'll be tough enough because I don't design easy courses."
He says it's an ideal opportunity for the European breeders to market their horses as well as boost the standard of showjumping in this country.
Hansen welcomes the persistent rain, saying it'll soften the surface especially for the European mounts.
Englishwoman McNaught, he says, is married to Duncan McFarlane, someone Hansen rode against in his heyday, and the couple have settled in Taupo.
She is second in the World Cup Series leaderboard, behind Laurie and will be competing in the Fiber Fresh Christmas Classic Jumping Championship next weekend in Taupo where Hansen will also design the course.
It is one of only seven premier shows on the national jumping circuit and more than 900 horses are expected to compete there.
Matheson is delighted with Hansen's course this weekend.
She was also in the Kiwi team last year when they beat the Aussies.
The youngsters, under chef d'equipe Richard Sunderland, of Tauranga, then got on to borrowed mounts at Camden, south of Sydney, to win the Transtasman Challenge at the Australian Youth Show in October following a loss on the opening day of the three-day event.
For Matheson, a second-year finance and accounting degree student at Massey University in Palmerston North, keeping the fire stoked for her sport is putting heat on her academic goals.
"I do sometimes think, I've got too much on," she says, shovelling sand and moving horse Cheltenham to a drier spot while talking on her phone.
"I fit things in but my study suffers when I've not done enough."
In many respects, she accepts she's her own worst enemy.
How much time does she allocate to equine interests?
"Probably too much on riding, actually."
She has been taking two horses to competitions but that has mushroomed to four.
"I'm riding a couple and schooling the rest for other people."
The temptation is to take a groom and her mother, Lesley, working for a chaff supplier in Hastings, is the first port of call.
"She's usually busy with her work but she's quite happy to be a groom for me," she says with a laugh.
Her father, Peter Matheson, and mother are supportive of her equine pursuits but the significance of studying isn't lost on her. "If I don't have something to fall back on I'll be pretty screwed," says the former Karamu High School student.
But she isn't shy to let herself drift into that world of escapism.
"I guess if I win Lotto, all of a sudden, I'll dump my studies."
