Constant N_INERTIA_PARAMS 

pub const N_INERTIA_PARAMS: usize = 10;

Number of inertia parameters per body: [m, cx, cy, cz, Ixx, Iyy, Izz, Ixy, Ixz, Iyz] — mass, COM (body frame), inertia about the COM. The packing (and the symmetric off-diagonal convention) matches vcad’s BodyMassProps::scalars() so a phyz gradient drops into the vcad seam unchanged.