The following tunes are good recommended base tunes for your RACER X FPV builds. Since are designs are universal kits that can be built with so many different types of flight controllers, motors, props, and other components, each build will vary. We now suggest using BetaFlight 4.1.x or higher. We have had great luck with tuning micros since the release of BetaFlight 4.1.x. In the past we recommended 3.5.7 since newer versions were typically designed for larger 5" quads and micros had lots of issues. Feel free to also join our "TWIG Builders" FaceBook group page to ask for help and share your tunes. The "TWIG Builders" FaceBook group was created to help others and share your custom builds with others.