Scott Atherton says he’s “optimistic” of achieving capacity grids for next year’s Rolex 24 at Daytona and Mobil 1 Twelve Hours of Sebring, with a large presence of international entries expected as part of its ‘Florida 36 Hours’ initiative.

Both events, which will open the 2018 IMSA WeatherTech SportsCar Championship season, are set to see entries capped to 60 cars, according to the IMSA President.

“We’ve had situations where we’ve started more but right now that’s a self-imposed cap,” Atherton told Sportscar365.

“There’s been a lot of interest out of Europe. The 36 Hours of Florida has caught a lot of people’s attention, even if the incentives are not seen as being over-the-top. If nothing else, it’s got people talking.”

The Prototype class alone is likely to see in excess of 20 cars for Daytona, with 15-16 full-season entries a “very realistic” possibility, according to Atherton.

Notable additions for next year include the pair of Team Penske Acura ARX-05 DPi cars, along with new or additional LMP2 entries from JDC-Miller Motorsports, CORE autosport, D3+Transformers Racing, BAR1 Motorsports and Performance Tech Motorsports.

Atherton admitted they could end up facing the situation of turning away entries for the two major endurance races, for the first time since 2014.

“It’s happened before. It’s not our of the question,” he said.

Entries for Daytona and Sebring would be prioritized by full-season “premium” entrants, followed by those committed to the full Tequila Patron North American Endurance Cup, and then single-race entries.

Atherton admitted they wouldn’t necessarily take Prototype entries over GT Le Mans and GT Daytona cars.

“You want to have a healthy mix of both,” he said. “But then if it’s a Prototype driven by a high-profile international superstar, all things equal, that’s going to get priority!”

While rumors of Jenson Button, or potentially Fernando Alonso, making their Rolex 24 debuts have continued to make the rounds, Atherton said planning for the two events has continued to intensify.

“We meet as a group, the management team, every Tuesday and those statistics are part of our weekly meeting,” he said.

“Right now there’s a lot of unconfirmed, but expected numbers we’re working with.

“As the days and weeks go by, those numbers will firm up.”