Hi, I noticed that the breakingForce & breakingTorque are not set in the cfg's for the mk3 parts. As a result these craft are very fragile. For example the following craft with almost no fuel and no payload needs to land with a vertical velocity of about 1m/s other wise it will fall apart. Copying the breakingForce & breakingTorque for 3m parts into the cfg's for equivalently sized mk3 parts appears to make the craft behave more consistently. Example ---------------------------------