NACA tech report on fin flutter | Rocket body discussion | Forum

Just pointing people to a handy resource for OHKLA design: here's an old NACA paper (NACA was the precursor of NASA) on the subject of fin flutter at supersonic velocities.  I'd been doing some searching on fin flutter in general and this seems to be a very widely cited paper.  It gives equations relevant to figuring out how thick your fins have to be, given their material's shear strength, to ensure they will remain rigid and attached during flight.