The Shute Shield standout was cut after a pre-season with the Waratahs earlier this year, claiming he was told he was "too short" to cut it at the next level.
But the 27-year-old, who still spends his "day off" each week on the tools, was enticed by the development pathway on offer at Ballymore and has fired shots ahead of a spicy reunion at Suncorp Stadium.
"I was just told (by the Waratahs) I was too short, but it's something I can't change and it's why I've got different factors to my game where my height's not needed as much," Vest, who will start on the bench on Saturday, said.
"It's really driven me to push myself to the next level.
"When I get on the field I'm just going to go to a dark place, put myself in a dark hole and just really try and prove to DC (Waratahs coach Darren Coleman) what he's missed out on.
"I'm grateful for Thorny (Reds coach Brad Thorn) to give me the opportunity to even get back at DC."
Vest ironically pointed out that his former Northern Suburbs captain Hugh Sinclair, who will slot into the Waratahs' second row on Saturday, is shorter than him.
"Hopefully he's still on the field when I get on and there might be a little bit of love in the rucks, we'll see what goes on," Vest said.
Thorn said pigeon-holing players based on their measurements was a mistake, pointing to the rise of Wallabies centre Hunter Paisami as another example.
"Hunter was too small - garbage," he said.
"Have a look at him, that's what he got told. Connor may be an inch shorter than me and I played at Test level.
"You have your strengths, you bring them out.
"Playing next to Alfie (Langer, for the Brisbane Broncos) taught me that; the smallest guy you'll meet and probably the best player I ever played with.
"These (stories of player perseverance) are cool, I love these ones ... when these guys come through they know the value of a dollar."
Coach Coleman and centre Izaia Perese (both COVID-19) will miss the game, with Welsh veteran Jamie Roberts to start at No.12 and inexperienced halves Jack Grant and Tane Edmed to combine for the first time.
Tate McDermott (ankle) is back for the Reds, who were relieved when Taniela Tupou's proposed two-game suspension for a dangerous clean-out was reversed by the judiciary.
"I had some words I was going to say if it'd gone through; I would have been really unhappy about that," Thorn said of the Tupou verdict.
"It's good that common sense prevailed.
"If you're going to make rulings around that sort of thing then you need to change the name of the game, call it something else.
"That was a very good clean out ... the people and players enjoy that physicality. You don't want to lose that."
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