Romain Grosjean will abandon his Melbourne-spec Haas VF-19 at Spa this weekend and join teammate Kevin Magnussen in using the US outfit's current-spec machine.
While Haas continued to implement upgrades on Magnussen's car over the summer, Grosjean reverted to the VF-19's early season aero package, a separation that allowed for a back-to-back comparison of the two specifications.
"For Spa, we will go with the upgraded car, which we [first] ran at Hockenheim," revealed Haas boss Guenther Steiner.
"We’ve learned quite a bit out of it and tried to improve the car by changing some of the components. Both cars will be the same spec, and hopefully we can still learn more about it."
Development is likely to start winding down for Haas as the team progressively switches more of its resources towards its 2020 contender.
However, improving the understanding of its current car is crucial to next year's design.
"The focus has already switched, partly, to the 2020 car," added Steiner.
"We need to see what we can come up with in the wind tunnel, with the small developments we do there for the 2019 car, and if we bring any upgrade kits. We don’t know yet."
Haas will start if Belgian Grand Prix weekend as the ninth team in the Constructors' standing, but just 17 points behind fifth-place squad Toro Rosso, a spread that reflects once again the fierce battle taking place in F1's midfield.
Steiner isn't banking on a spectacular run up the ranks in the second part of the season, but the Italian won't dismiss gaining a few spots.
"Everything is possible, but it is difficult as our car doesn’t perform well in races, and that’s where you score the points," said Steiner.
"Nevertheless, we will be trying hard to pick up whatever we can. Hopefully, we can get a few more results, and then we’ll see how we end up in the standings."