"It was a perfect net score, but I rated myself 95 per cent at that regatta," he says. "There was still some places where I can improve - the execution of the starts and having more fluency in key moments."
Leith's sensational sailing at Mexico will make him the favourite for the 45-54 age group at the World Masters Games Laser event to be sailed close to his training ground at Torbay.
"April is one of the harder months to predict for breezes at Torbay," he says. "The heat on the land might not be hot enough to bring the wind in - it could be anything.
"I'm hoping for a storm. I'm better with a breeze above 10 knots, but I will be prepared for all conditions.
"Normally, I'm travelling overseas for world championships. This time, I will be getting out of my own bed to go sailing, and it will be cool for my kids to come and watch me."
Two of his three children - 11-year-old Lucy and 9-year-old Joe - race in the Optimist class.
Leith, the Murrays Bay Sailing Club commodore, has entered the past nine Laser Masters World Championships and won six of them, finishing second twice and fourth.
One of his seconds was in Hyeres, France, two years ago and he wasn't happy.
"They [officials] changed the rules at the last minute and had only one race instead of two on the final day. I was pretty bitter about that - I thought I was good enough to win."
A former New Zealand Olympic triallist in the 470 class, Leith first competed at the world masters championships at Terrigal in Sydney in 2008 and will travel to Split in Croatia next year to defend his world title.
Leith won his first title in 2010 at Hayling Island, just off the south coast of England near Portsmouth, and went on a run of four successive victories, including a win in 2011 on the breezy America's Cup course, between the Golden Gate Bridge and Alcatraz.
He first sailed at the age of three alongside father Doug, who brought the first Laser to New Zealand. Leith renewed his taste for Lasers, watching the sailors scoot around Lake Pupuke, after he returned from London in 2004.
He worked there for six years, first as a specialist tax accountant for EY and then with investment bank CIBC World Markets. Away from the trading floor, he sailed with British skipper Alex Thomson in the famous 2001 and 2003 Fastnet offshore races.
Leith was the youngest executive director at World Markets aged 29.
"We closed some big, profitable deals, but I always knew I would come back home and live the dream. I now invest in my kids and I have the financial freedom to manage my lifestyle."
He has shareholdings in a civil engineering company in Hamilton and a car parts business in Manukau.
Leith competed in his first New Zealand Laser Masters Championships in 2007 and has won his age group for the past 10 years.
"The Laser is the most competitive and well-sailed class in the world. There are 211,000 Lasers around the world - the highest boat number per class.
"The Laser is simple but difficult to master. The boats are all identical with genuine parts - not like the America's Cup, which is a space race.
"It's sailor against sailor, not chequebook against chequebook. I just enjoy it and you have to get up for every race, even at club level."
Leith will complete a three-month training programme for the World Masters Games. He will cycle three or four times a week, visit the gym and sail for stretches of 10 successive days "hunting around for the windiest part of the bay".
He says Laser yachting is an endurance sport.
"People think you are just sitting on a yacht, bobbing on the water, but you are hyper extending in one position for an hour. Your legs and torso are locked in, you have to have good contraction and you are physically under the pump.
"I will smash it really hard on the first day, show everyone how good I am and get a good lead," he says. "Then the rest falls into place.
"I have learned to stay patient and grind my closest competitors down."
