Question: I need the rotated section properties for square HSS. The working cross-section is thus diamond shaped. Do you publish these section properties?

Answer: I am not aware of any published section property data for HSS (or open profile shapes for that matter) on sections with transformed axes. 

The moment of inertia (I) property is given by the AISC 15th Edition Steel Construction Manual Table 17-27 as I = I_xsin²ϴ + I_ycos²ϴ, which for a 45⁰ angle would result in I_rotated = I_x = I_y. For other section properties, as necessary, one might even consider calculating based on a sharp-cornered section; i.e. do not consider the effect of the corner radii. Of course, for the 45°-rotated section the cross-sectional area (A) and radius of gyration (r) also remain the same as for the un-rotated section.