Supercars approved a revised rear aero package for the Mustang ahead of this weekend's Townsville 500 in a bid to help find parity with the Chevrolet Camaro.
The tweaks to the rear wing and boot spoiler were expected to improve the rear stability of the Mustang and address rear tyre life issues that have helped the Camaro prove unbeatable so far this season.
Qualifying then hinted at an improvement, with five Fords and five Chevrolets in the top 10 earlier today.
However tyre life issues reared their head again in the race, the likes of Chaz Mostert and Cam Waters both complaining of rear instability and high rear tyre degradation.
Mostert did manage to rescue a podium with an aggressive three-stop strategy, but said even with fresher tyres at the end it was hard to run with the best of the Camaros.
"It was good to get P1 in class," he said. "Even at the end there, [Will Brown and Broc Feeney] just drove away.
"It's been a disappointing year. I've been hanging in there the best I can in the points, but to try and be in the championship, you obviously need [a Camaro]."
"It feels like we don't have a rear wing," he later explained. "We're okay in the slow, mechanical corners, but the really high commitment brake zones, and the high speed back section, the car just gives away. You've just got no rear at all."
When asked post-race if the updated aero package had made any difference, Mostert said: "I can't feel any improvement".
He also questioned the fact that Supercars relies on its real-world VCAT aero testing process instead of putting cars in a wind tunnel.
"I just think it's about doing stuff properly," he said. "Every other category around the world uses wind tunnels and does homologation processes to the best that they can.
"I don't know any other category that still runs cars up and down a runway to work out what's going on, to be completely honest.
"In the previous history of Supercars it's been pretty good, but this year it's been pretty light on the Ford side."
Waters led the first stint of today's race, and said he chewed through his rear rubber without even trying to gap the field.
"I wasn't trying to pull away or anything, I was trying to look after the tyre," he said.
"I got 20 laps into that [first] stint and I felt the rears go away and I just started bleeding time.
"Each stint was a little bit better with the track conditions cooling off, but not enough compared with the other guys.
"Well got through all the data. I think our qual car isn't too bad but we'll have a think about our race car and what we can do differently. It's been the story of our season, trying to find a bit of tyre life."
Tickford CEO Tim Edwards urged some patience with the new aero package as teams learn how to get the best out of it.
"We have engineered ourselves down a certain path for a certain aero balance, and that's changed a little bit," he said.
"We need to learn more about it and understand it. Yesterday we had two 30-minute practice sessions to try and undo what we spent six months getting to. We need a bit more time.
"We've got a test day coming up in a couple of weeks, so we're champing at the bit to get there and actually understand it a bit more, and hopefully dial the car in a bit better.
"We've got some good car speed but we've got to improve that rear tyre life."
