A weight penalty and the burden of history hasn't been enough to stop last year's Melbourne Cup winner Dunaden from retaining favouritism to go back-to-back at Flemington.

Racing Victoria chief handicapper Greg Carpenter penalised Dunaden one kilogram for last Saturday's Caulfield Cup win and the French stayer will now carry 59kg in the Melbourne Cup.

No horse has won the Melbourne Cup with 59kg or more since Rain Lover in 1969.

Rain Lover carried the equivalent of 60.5kg (9st 7lb) while only two horses in the metric era since 1972 have won the Cup carrying more than 57kg.

Despite those obstacles, Dunaden, who raced into Cup favouritism with his win at Caulfield, remains at the top of betting at $6.50 to become the sixth horse to win more than one Melbourne Cup.

He is favourite ahead of Mount Athos at $8.50 and the 2010 Melbourne Cup winner Americain at $9.

Last year's runner-up Red Cadeaux is at $10 along with French horse Brigantin who will make his Australian debut in Wednesday's Geelong Cup - the race which propelled Americain and Dunaden to their Melbourne Cup wins.

"It's a big challenge for him but he proved again on Saturday he's one of the best stayers in the world, one of the best stayers we've seen come to Australia and I think even with the one kilo (penalty), which equates to about two lengths in distance, that he's still going to be very hard to beat," Carpenter said.

Dunaden became the first original topweight to win the Caulfield Cup when he stormed home under 58kg on Saturday defeating Alcopop, Lights Of Heaven and Americain.

Carpenter said the quality of the field and "manner in which he won" the Caulfield Cup demanded a review of his Melbourne Cup weight.

"I am aware however that a new challenge awaits him in the Melbourne Cup," he said.