“We have performed extensive ground testing by comparing warm up times, full power tethered pulls, and overall temperatures in 100 degree environments against other aircraft as well as our Rotax powered Sonex as the “control” aircraft. We have been very pleased with the results… We took to the skies and tested the Onex and its installation. While we expected it to perform well, frankly, we didn’t expect to perform as well as it did. The flight went flawlessly. The plane is so well balanced, it would fly with or without a pilot (although we know that’s not possible). It did not have a heavy wing, cooling issues, or any issues to speak of. Very uneventful, which is what you strive for on a test flight.” Source: Cooper Aircraft Corporation has started offering expanded support for Rotax installations with a new mount for naturally aspirated engines on the Sonex series.