The horse forced to switch stables in the week of his spring grand final went within a bound of winning the Cox Plate.

And his jockey says it was the 9.5kg weight difference with three-year-old Shamus Award that cost him victory.

Happy Trails was transferred to trainer Byron Cozamanis on Monday after Paul Beshara was disqualified for six months after being found guilty by the Racing Appeals and Disciplinary Board of treating the horse on the day he was due to race last month.

Beshara is awaiting a date for his appeal, and it was left to his new trainer to put the final touches on his Cox Plate campaign.

"I thought he was going to get there. I got cramp in my leg," Cozamanis said.

"I must have been riding him."

Jockey Dwayne Dunn said Happy Trails would continue to be underestimated, but the horse again stood up in a big race having already won two Group Ones.

"I thought at the top of the straight I was going to run them down," he said.

"But he's got 59 kilos and the other horse has 49-1/2. That's the difference. Weight is a killer, but the horse is flying.

"It's not the right preparation for a race with everything that's gone on, but the horse has just stood up and been counted."

Dunn considered himself unlucky not to win a Cox Plate two years ago when Rekindled Interest was a luckless third to Pinker Pinker, and he said this was "another hard one to swallow".

"At least there was no bad luck in running today," Dunn said.