Checks Euler column buckling and local wall crippling, reporting the weaker mode. Supersonic check adds beam-column interaction: angle of attack creates bending moments that combine with axial compression, with amplification from the P-delta effect. A 0.6x transonic derating accounts for shock waves and flutter. CNα = 2 (slender body theory). Real-world limits also depend on fin attachment, glue joints and construction quality.