The thickness of Formula 1's halo cockpit protection device could be reduced as the FIA plans to "see how much we can push" the controversial design.
It will be mandatory for teams to run the halo from 2018, after the FIA picked that device over the shield that was tested on-track at Silverstone last month.
The criticism of the halo is mainly for aesthetic reasons, although race director Charlie Whiting said he expected the visual appeal to improve when the design was finalised.
In addition to teams being able to apply aerodynamic fairings, the FIA is testing a revised version of the halo with a narrower central pillar, with the aim of improving forward vision.
The likelihood is that it will ask teams to try it on track later in the season.
"The central strut is currently 20mm," explained FIA safety director Laurent Mekies. "We feel that we have scope to reduce that thickness for the benefit of the drivers' forward vision.
"So we will be testing before next year, going as low as 16mm, and see how much we can push it."
The halo returned to the track in Hungary on Wednesday for the first time since its 2018 implementation was announced, with Mercedes test driver George Russell sampling the device.
Teams are keen to gain more experience with it as they study the impact on aerodynamics, especially the flow into the airbox.
The FIA has given permission for teams to conduct further track tests before the end of the season, including on race weekends.
"We've told some teams that have asked that they can use them during FP1 and FP2," said Whiting. "And during in-season tests.
"Not [Pirelli] tyre tests, but for example the two-day test here [in Hungary] - we said they could use them at this test, the test after Abu Dhabi, and in free practice sessions on the first day at any event, as most of them did last year."