Since the introduction of the current regulations in 2022 it has been apparent that the Milton Keynes team has gained more straightline speed than others with an open DRS.
Like all teams, Aston Martin has worked hard to catch up, with the latest iteration rear wing seen on the AMR23 at the Abu Dhabi GP last month.
"We noticed Red Bull were very strong at that last year, so they sort of took the march on that," said McCullough. "I remember Jeddah last year was the first time everyone was going, 'Wow, that's quite a big DRS switch.'
"The interaction between the whole back of the car, and the loading on the diffuser, the beam wing, the rear wing, the main plane, the flap, the brake ducts, the interaction of all that's obviously quite different to previous generation cars.
"And getting a stable aerodynamic platform that we don't have porpoising and all those other things that we don't want, getting lots of load, but getting it that when you open the DRS that you have as big as reach as possible is the aim.
"We didn't have a particularly strong one to start off with, and we were just systematically developing to increase that whilst trying to retain stability."
McCullough says it has not been easy to optimise the DRS switch given the compromises involved.
"So all those elements of the back of the car are linked," he said. "There's only so much you can do within the regulations. You're always trying to produce downforce and not have too much drag.
"But then on top of that, to get the DRS switch and get all those things working well, it is a challenge for the aerodynamic teams.
"And that's why you've seen quite a lot of development in that area, not only by ourselves, but by other people too."
Regarding the wing trialled in Abu Dhabi, he said: "For us, it was important to get it on the car the end of this year just to correlate what we see in the wind tunnel and CFD, and we did some cross-car, cross-session compares, and the wing is performing well."
