In-form Impasse will make his open company debut at Eagle Farm despite weights for the race being lifted.
Impasse was accepted in Saturday's Family Raceday Open Handicap and the Class Six Plate, both over 1400m.
When the original topweight Hallelujah Boy did not accept in the open handicap, weights were raised 2.5kg meaning Impasse was lifted to 56.5 kg.
It left Dunn with a tricky decision as Impasse looked well placed in the Plate race in which he drew barrier one.
In the end Dunn decided Impasse was going so well he would tackle open company.
"I don't know why they don't follow NSW and when there is no longer a genuine topweight they re-handicap the entire race," Dunn said.
Impasse has attracted most attention to date because of his breeding.
He is by 2011 Golden Slipper winner Sepoy out of Amelia's Dream who was ruling favourite for 2008 Golden Slipper before being retired because of injury.
Impasse is now the best-performed of her offspring with six wins and seven placings from 21 starts.
But Dunn believes the gelding is now ready to be recognised more for his own ability.
Impasse was originally trained by Chris Waller but has been with Dunn this campaign for a second and a last-start Eagle Farm win.
"He seems to be in a good head space these days and enjoying the change of scenery to our country stables," Murwillumbah-based Dunn said.
"The 1400 metres suits and he will go on to something a bit better after this."
Robbie Fradd will partner Impasse who is one of a good book of six rides for the veteran jockey.