There will be something different about Catkins before the Sheraco Stakes that Chris Waller concedes will threaten her outstanding first-up record.

For a racemare which often carries the hard-earned cash of those with a liking for short odds, it will be a burden of another kind that could be against her at Rosehill on Saturday.

It all has to do with the size of her girth as she prepares for a showdown with New Zealand Group One winner Bounding and Peeping, an emerging sprinter for Ron Quinton.

"I wouldn't be surprised if she needs the run ... she's just that little bit heavier because she's done a bit well," Waller said.

"She is still blowing after her gallops even though she has trialled well.

"I would expect her to race above her fitness but there is still improvement to come."

Catkins' six first-up victories in seven campaigns include her success when odds-on in last year's Sheraco Stakes, a win that counts as one of the easiest of her career.

She will be at a much more backable quote on Saturday with Bounding a rightful pre-post favourite and Peeping a a genuine threat, according to Waller.

"Bounding and Peeping are good horses, serious horses and they have had a run under their belts," he said

At her first start for Peter and Paul Snowden, Bounding trounced a tidy field of sprinters in a Group Three race at Caulfield.