Group One winner Bon Aurum is yet to win over 1600 metres but trainer Ciaron Maher remains confident it is within the horse's capabilities as he prepares him for the Cantala Stakes at Flemington.

Four of Bon Aurum's five career wins have come over 1400m while he has had three starts over 1600m, all in Group One races.

"I'm still confident that he'll run the mile," Maher said.

Bon Aurum won the Group One Sir Rupert Clarke Stakes (1400m) two starts ago at Caulfield before his last-start sixth, beaten less than two lengths, in the Toorak Handicap (1600m).

Maher has changed Bon Aurum's work around since and believes the four-year-old is in better order going into Saturday's $1 million Group One Cantala Stakes than he was leading into the Toorak.

"I think the Rupert Clarke probably took a little bit out of him and he just seemed OK going into the Toorak," Maher said.

"I've just changed his work around a little and he seems to have really responded.

"I've backed off him a little bit and really got the confidence up in his work."

He said because he was a big, strong stallion Bon Aurum took a bit of work to get fit for those Group One races earlier this spring but he has now been able to back off because he is at peak fitness.

"I think he's really improved. He loves Flemington and he gets in with a nice weight of 54 kilos."

Bon Aurum has drawn the second outside barrier in a field of 16 and one emergency but Maher noted some of the horse's best wins have been from wide draws.

"He like to sit in that three-wide line and roll into the race and Flemington really suits that," he said.

"He'll need a bit of cover, need a bit of luck, but he's in good order."

Bon Aurum is at $26 with Group One Ranvet Stakes winner The United States the $5.50 favourite as he prepares to back up after his convincing win in the Crystal Mile last Saturday at Moonee Valley.

Toorak winner He's Our Rokkii is at $6.50 ahead of three-year-old Seaburge and four-year-old Palentino who are both at $7.50.

Palentino has already won the Australian Guineas and Makybe Diva Stakes at Group One level over 1600m at Flemington this year.