Rear end aerodynamics are a key change to this year's technical regulations, with the aim being to pare back downforce given the carryover of tyre specifications ahead of the switch to 18-inch wheels in 2022.
While the reduction in the floor area is perhaps the most obvious element of the changes, the height of the diffuser strakes has also been cut by 50mm.
However, the latter only applies outward of 250mm from the car's centreline, an aspect of the regulations which McLaren has chosen to take advantage of by keeping the longer strakes in the area where allowed on its MCL35M.
Key reasons that the Woking squad's design is “straightforward”, rather than some form of trickery, and thought other outfits might opt for something similar.
“It is a normal design idea, and actually I think we are a bit surprised that maybe we're the only team with that,” he said.
“It's just one feature of many in an area which changed for this year.
“You've got a certain regulation of a continuous surface in that area within the Y250 position, either side of the centreline of the car.
“Those little vortex generators down there which you see as well on pretty much every car now, these little aluminium or carbon parts are actually governed by de facto the same rule.
“So, it's fairly straightforward.
“You need the CAD screen to see it, because you're taking cross sections of a 3D surface, so it's fair to question I suppose when it's difficult to tell without that CAD data to prove it's within the boxes it should be in and to prove it's a continuous surface. But that's really all it is.”
Key believes that a team could copy and implement the McLaren solution, should it see a benefit from doing so, in three to five weeks.
“I think the first port of call with any idea you see out there is CFD, so I think you can jump on an idea that you spot on another team within a week easily nowadays,” he explained.
“I guess if there's still interest after a week, whether it's our diffuser or Mercedes' edge of floor detail or whatever it is, I think you can get a feel for things quite quick.
“Then it's really understanding how it works with your car. That's the key to this.
“You can then end up with a unique geometry of your own because you might understand the principle, but then you have to adapt it accordingly that it works with your car.
“The diffuser situation for example is also very stable in that environment as well.
“So you'd probably therefore wind tunnel test it, which might be a week or two down the line, and then you've got to manufacture it. These particular steps are pretty straightforward.
“So, you could say between three and five weeks between taking the picture and putting it on the car if you really wanted to push this through.”
Key also gave credit to the team at McLaren for identifying the solution that others seemingly did not.
“I think it's always nice for a team to come up with an idea which is unique and the credit fully goes to our aero department and the guys in the rear aero group for realising that there was an opportunity there to use the new regulations in such a way,” he remarked.
“I suppose it's one of the visible things which gets talked about a lot, but ultimately it's just a bit of a much wider picture of a complex part of the back of the car.
“I'm sure it'll be forgotten by the time we get back here in a couple of weeks' time.”