"He has also had life experiences with a degree of similarity to Ariki, so he could draw upon those to help his portrayal."
In his younger years based in Christchurch, Hapi was a member of a gang. It took him about five years before he broke ties with them in 1997. Not that he regrets those years.
The reformed father of six is philosophical about how those experiences got him where he is now, both personally and as an actor with a big role in a major film.
"If I didn't have all that stuff to draw on I don't think I could've got the part," he says simply.
"I don't want to draw any unnecessary attention to that whanau because they're still my whanau. They were a big part of my life."
Their response is likely to be one of awe and respect for the power of Hapi's portrayal of a man who pushes his eldest son into his gang out of a misplaced desire to see him safe and secure.
The dysfunctional nature of their relationship, augmented by the fractious bond with his brother, psychiatric patient and chess whizz Genesis (Curtis), isn't too far from Hapi's own family experience, although he's understandably reluctant to discuss this.
"Mum and Dad didn't stay together so my mum left me with my grandmother," he explains. "But I don't want to go there because I don't want to get all teary. It's a whole other lifetime."
Born in Murupara, east of Urewera National Park, and raised by his staunchly matriarchal grandmother until he was 14, Hapi, Tuhoe on his mother's side, Whakatohua on his father's, was on a Winz computer course when he got wind of the Dark Horse role.
Mostly skilled at physical labour, with a modicum of acting knowledge from a couple of courses, he jumped at the chance to audition, memorising his lines like a seasoned pro.
Adding poignancy to his experience on the film, Hapi also tracked down his mother, Robyn Belmont, through Facebook, making contact with her for the first time since 2000 and inviting her to walk the red carpet with him at The Dark Horse's premiere at Auckland's Civic Theatre a week ago.
It was an emotional reunion. "She goes, 'How will you know what I look like?'" says Hapi.
"I say, 'Hey, you're my mum. Nobody forgets what their mum looks like.'
"We had some time together before the premiere and she's like, 'I don't believe this is happening. I'm so proud of you.' And she hadn't even seen the movie. I saw her crying a few tears during the film.
"We spent a lot of time looking over at each other and for both of us it was like we hadn't spent all that time apart. There wasn't a day when she didn't run through my thoughts, and she said the same.
"Then she never said nothing about the movie till she was getting ready to head home to Dunedin, and she says, 'Son, I'm proud of you.' That's all she needed to say."
Hapi will be seeing the film with his mum again tonight, in Dunedin at a charity screening for the Kokiri Training Centre, where he worked with underprivileged kids before his move to Manukau.
"So I get to introduce her to two of my kids and her great-great-grandsons."
The Dark Horse opens nationwide on Thursday.
