The strength tests Formula 1's new halo cockpit protection device must be put through are "pretty scary" and prompted some "heart-stopping moments" because of the loads involved.
F1 teams have found it complicated to ensure that their cars, with the mandatory halo device fitted, are strong enough to withstand new FIA crash tests that include one with a vertical load of 116kN.
Mercedes technical director James Allison revealed last week that the forces that the halo has to cope with are the equivalent of placing a London double-decker bus on top of the car.
Now, McLaren's chief engineering officer Matt Morris has explained that his team had to make unexpected changes to its chassis after encountering some problems with early mock-up designs.
"It has been a big challenge," said Morris. "The loads are very, very high.
"We always knew it was going to be a challenge and we invested some time and money up front to do quite a lot of test pieces.
"Obviously you don't want to build a complete chassis, but we built various test pieces where we had dummy halos, parts of halos, full halos, and testing how the interfaces would behave.
"We found some issues but we planned early enough so we could react to those issues and catch the main chassis, which we did.
"It was close. I am not saying we breezed through it, and there were quite a few heart-stopping moments when doing the static tests that comes in from an oblique angle - where it takes the weight of a London Bus.
"When you see that test going on it is pretty scary with the amount of load going in there."
Morris said that the extremes of the test means it is possible that some outfits may hit trouble trying to get through.
"It will be interesting to see if anyone has any problems," he said. "It is a pretty tough test so it wouldn't surprise me if people have issues.
"I hope they don't because we want everyone in winter testing, but it has been an interesting challenge."
Morris also explained that the allowance of fairings and the way the halo is incorporated around the rear mounts may mean different teams' designs "may look a little bit different cosmetically".
McLaren's aero chief Peter Prodromou thinks there could some interesting solutions as teams work on minimising losses in this area.
"Aero wise it is certainly not penalty free, so I think there is a challenge there to either cope with it in the first instance, let's call it damage limitation, and afterwards think about opportunity and exploitation," he said.
"It does open up some avenues that possibly are interesting to look at - and I am sure there are going to be a variety of different solutions out there.
"The scope is quite limited as you have this allowance around the basic shape, but there is opportunity there for aerodynamicists."