Champion trainer Chris Waller has thrown his support behind Kathy O'Hara who rides lightweight hope Madam Rouge in the Group One Galaxy.

Madam Rouge, the winner of three of her past four starts, has 51kg and Waller says O'Hara can get the job done.

"I thought long and hard about what jockey to put on and it came down to the following reasons, and that's simply because Kathy continues to ride in Sydney each Saturday," Waller said.

"She is respected by her peers, she's a strong jockey and also a natural at the weight.

"The option is, do you put a higher profile rider on and then bank on them losing a couple of kilos and still being as sharp, not just physically but also mentally?

"Kathy has actually won on the horse prior to her impressive Magic Millions win so she's got experience on the horse and I'm rapt to have her aboard.

"From the draw (three) she is certainly going to get a nice run and she looks to be a genuine Group One-winning chance."

O'Hara won the Listed Christmas Classic on Madam Rouge two starts ago and will be chasing her third Group One win in Saturday's Galaxy (1100m) at Rosehill, after the 2012 Coolmore Classic on Ofcourseican and 2016 Vinery Stud Stakes on Single Gaze.

Stewards will allow Billy Egan to ride Miss Leonidas 1kg over her 51.5kg handicap while Tim Clark can also ride I Am Excited 1kg over her 51kg.

If first emergency Cosmic Force gains a start, Glen Boss is able to ride the colt 0.5kg over his advertised weight of 50kg.

If Cosmic Force does not gain a start, Boss will be aboard the Joe Pride-trained Fasika who has 51kg.

Apprentice Robbie Dolan is booked to ride filly Anaheed for the Peter and Paul Snowden stable at 50kg but will switch to third emergency Splintex, trained by his boss Mark Newnham, if the colt gets a start.

Like Cosmic Force, Splintex is a dual acceptor in the Listed Darby Munro Stakes for three-year-olds on Saturday.

Minimum weights in NSW will rise 1kg from Monday to help assist jockeys with their weight and health during the coronavirus pandemic.