McLaren's chief engineering officer Matt Morris says there were quite a few "heart-stopping moments" as McLaren's Halo was put through its tests.
With the FIA declaring that Formula 1 will use Halo in 2018, the teams' designers were put to the test incorporating the cockpit protection device.
Trying to keep the weight down while ensuring that the Halo could cope with the massive loads required wasn't always easy.
Mercedes tech boss James Allison recently described it as having to take the weight of a London double decker bus while Morris has admitted it caused a few moments of worry for McLaren.
"It has been a big challenge," Morris told Autosport. "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 test 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, which it is designed to do."