Watch: Denise Gough and Kyle Soller discuss Andor villain costumes
Both stars play middle-manager Imperial officers in the series, with each of them fighting to prove themselves by tracking and shutting down insurgent groups of rebels.
Set before the events of 2016 film Rogue One, the show traces the early anti-Empire activities of Cassian Andor (Diego Luna) and his recruitment into the Rebel Alliance.
Gough revealed to Yahoo that she and Soller made similar requests at their costume fittings in order to enhance their sinister performances.
She explained: "As both me and the character, I wanted to make sure that her uniform was nipped and pulled in and the boots were a little bit more and everything is super sharp.
"Then she will stand a certain way so there isn't a single crease on the front and anyone she sees [slouching] just drives her crazy.
"When I was told by the designer that Kyle had done the same thing, I thought 'we're gonna be just fine'."
Read more: Everything we know about Andor
Soller said his costuming was "100% effective" in helping to construct his ambitious, desperate young office climber Syril and that he wanted his "specific tailoring to be perfect".
"[Creator Tony Gilroy] had written these characters so wonderfully fully-fleshed. A mix of light and shade and very complex and relatable," he said.
Soller added: "They're two people who actually don't listen to the word 'no' from their superior officers. That's extremely dangerous when you're putting that within the fascist regime."
Gough said that Syril and her character Dedra are "not just baddies", but are prepared to go to "quite extreme" lengths in order to raise their status within the Imperial hierarchy.
"If you're in a Nazi or a fascist regime and your end goal is to get to the top of it, you're probably gonna have to do some pretty awful things to get there," she said.
Gough added: "They're rebels within the regime. They're doing things like getting around and going under the rules and bending the rules.
"Dedra gets in serious trouble for something that she does in order to prove that she's right about what's happening. It turns out okay, but she could be killed for going against the regime, even if it's for the protection of the regime.
"They're staging their own individual rebellions within the Empire, which is why all of these characters are so interesting."
Following a number of figures within the Rebellion and the Empire, Andor has an ensemble cast around Diego Luna's title character, including Adria Arjona, Stellan Skarsgård and Fiona Shaw — with Genevieve O'Reilly and Forest Whitaker reprising their roles as Rebel leaders Mon Mothma and Saw Gerrera.
Andor will debut on Disney+ with the first three episodes on 21 September, followed by weekly episodes in subsequent weeks.
Watch: Trailer for Disney+ Star Wars series Andor