[5] In 2013, Palmer was given the opportunity with GMG Racing to compete in the final rounds of the Lamborghini Super Trofeo Championship in North America.

[7] Also in 2014, Palmer filled in for an injured Seth Neiman and drove for Flying Lizard Motorsports in the WeatherTech SportsCar Championship Road America round.

Later in the year he returned to the team to compete in Petit Le Mans with co-drivers Spencer Pumpelly and Nelson Canache.

In January 2015 he was offered an official contract from Lamborghini to drive one of the factory cars in the 2015 Blancpain Endurance Series.

[9] In addition to driving for the factory supported Lamborghini program in Europe, Palmer also competed in the endurance races in the WeatherTech SportsCar Championship for PR1 Motorsport alongside Tom Kimber-Smith and Mike Guasch where they had an almost perfect season winning their class in the 2015 24 Hours of Daytona, 2015 12 Hours of Sebring, and 2015 Petit Le Mans.

During May 2016 Palmer was injured in a major accident during warm up in the Pirelli World Challenge at Lime Rock Park, suffering a head injury.