Proton Ford driver Ben Barker explained that it was "a bit of a surprise" to head Wednesday evening's qualifying session, which determines the eight cars that will battle for pole in Hyperpole on Thursday, in the most competitive showing for the Mustang since making its debut in the World Endurance Championship this season.
His comments were echoed by the boss of Ford's technical partner Multimatic, Larry Holt, who told Motorsport.com that his expectations were exceeded when Barker clocked a best time of 3m55.263s that put him 0.143s quicker than Frederik Schandorff's Optimum-run Inception Racing McLaren GT3 EVO.
"Did I expect what happened? No, I didn't to be honest," Holt said. "I had a good confidence we would be top five or six."
Holt revealed that "we're making big, big chunks of progress at every race" and reckons its struggles with kerb-riding and optimising the mandatory FIA torque sensors are "all sorted out".
As a result, and following an encouraging two-day test at Watkins Glen last week, Holt said he was quietly optimistic that the Mustang could shine at Le Mans because its high centre of gravity relative to class rivals is less of a factor than at regular WEC tracks.
"I had high expectations that we were going to show better than anywhere we have," he confirmed.
"It's just that one weakness of the car isn't as important here."
Expanding on the car's CoG, Holt added: "Here there's only two or three places where it actually raises its ugly head.
"There's only a few places where we actually suffer that weakness. Everywhere else, we're good."
Barker said that he had been given a tow by fellow Ford factory driver Christopher Mies for the lap before his benchmark effort, but maintained his "top speed wasn't exactly ballistic, we're all quite level with other cars".
"It means that we really found something – found some more performance through the corners, which is great," the Briton said.
"The car had been feeling good on the lead up to qualifying, in the practice sessions. I felt quite good with the balance.
"I would have felt that, having felt the balance we had, if we were far off then there was more of a serious issue.
"It's a nice place to show our credentials, and hopefully we can continue that into, obviously, Hyperpole and then the big race."
Holt is confident in Ford's reliability for the race and said early problems with the rear-diffuser coming loose after contact has been resolved by "a slight moulding change".
"Reliability is a big deal and we've really had really good reliability with the car," he remarked.
"It's screwed together well, it was well-engineered and I think that's an advantage. And I got a smart bunch of drivers."