Weight has ruled Dwayne Dunn out of the ride on Myer Classic favourite Stay With Me and the jockey instead turns rival in the Group One race on Politeness.

Dunn rides the Robert Smerdon-trained mare in Saturday's Myer Classic (1600m) with three-year-old Thousand Guineas winner Stay With Me to be partnered by Sam Clipperton at 49kg.

The challenge facing Stay With Me, who Dunn has ridden in her four spring starts, is whether she can match it with the older horses early in her career, while Dunn believes Politeness's biggest query is the distance.

Politeness has stormed home to win twice at Group Three level over 1200m this campaign and steps to 1600m.

Dunn rode Politeness twice last preparation and reunites with her in the Myer, believing the five-year-old is going better this campaign.

"I got to work her on Monday at Sandown and she's working really, really well," Dunn said.

"Probably the chink her in her armour is two tries at the trip for no result yet.

"But Robert has done a lot of work with her. She's been well schooled for this race and she should run well.

"My race is about how I get Politeness to switch off and into a nice rhythm to be able to sprint well."

Politeness will also be trying to win at Flemington for the first time in eight attempts.

Stay With Me is the $4.50 favourite to become the first filly to win the Myer Classic.

Five have tried with Alinghi going closest when second in 2004.

"She's very hard to line up because it's her first time against the older horses," Dunn said.

"I know she gets a great weight relief, but she has drawn wide and has probably got no option but to go back.

"I know how good she is and I'll be very keen to know where she is in the run because she's going to have some sort of finish there at some stage.

"But it's hard to line her form up."

Royal Descent ($5) has blinkers on for the first time as she bids to bounce back from a Caulfield Cup failure.

She was trapped deep from a wide barrier and Waller said the run wasn't as bad as it looked.

"Glen Boss shut her down when it was obvious she couldn't win and didn't punish her," Waller said.