I just ran two frequency studies on the same assembly with no restraints (to get the rigid body modes) with the only difference being that one used the default mixed shell and solid mesh and the second had all solid mesh (manually selected). The results for the mixed mesh model indicated a non-rigid mode as mode 4 with a frequency of 70Hz. The results for the solid mesh model indicate a non-rigid mode as mode 7 with a frequency of 521Hz.Has anyone else noticed this difference and which is considered to be accurate?