Kevin Magnussen and Sergio Perez have added new questions around the practicality of the Halo and voiced concerns about it after the latest trials at Monza.

Perez, along with Kevin Magnussen and Jenson Button, all tested the Halo concept safety device during installation laps in FP1 at the Italian circuit.

Despite being pleasantly surprised by the visibility the Halo gave around Monza, Perez says he'd be concerned how quickly and safely a driver can get out a car with the Halo device attached.

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To date, no official test have been carried out on how the current concept performs in a crash or when a car overturns which is an area Perez wants the FIA to prove before making it mandatory for all F1 cars in 2018.

"Visibility-wise it was quite good, to be honest that surprised me, but I'm not totally satisfied with getting out of the car," Perez said. "My concern is how slow you get out. It takes a good five seconds more than without the halo, so it makes me feel a bit uncomfortable that I need more time to get out of the car.

"I still think there is more work to be done in that area to try and get us drivers out of the car as quick as possible. That's definitely a concern. You are sitting in car and you know it's going to take five seconds longer than without the halo. If you are in a critical situation five seconds can be a lot."

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Magnussen, who is yet to drive with the Halo, has come out against the cockpit protector and feels the FIA will be able to produce a unit which is safer and more aesthetically pleasing than its current concept.

"If I could choose I'm not going to run it," Magnussen said. "I don't think it will come in. I don't think so. I think now they've delayed it they will come up with something better.

"They need to come up with something better. The Halo isn't going to go on. If it was then it would come on next year. They've obviously seen that they can come up with something better and they need more time to do it."

After a vote not to use the Halo device for the 2017 F1 season it is believed the FIA will use the extra time to continue its development and aim to introduce it in 2018.

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