Pre-submission Draft keeps the conservative two-channel fc diagnostic framework and selects aluminum/lead (Al/Pb) as the primary conceptual material-pair candidate for the scalar channel. The reason is practical rather than theoretical: aluminum is safe, inexpensive, machinable and effectively mono-isotopic, while lead is dense and provides a larger toy composition contrast than the earlier Be/Pb pair when paired with Al. Beryllium is no longer recommended as a first experimental material because of occupational health and handling risks. Al/W remains the preferred lead-free backup candidate. The proposed material-pair test is still framed only as a conceptual precision-composition estimate, not as a completed Cavendish apparatus design. The central theoretical question remains whether the scalar channel survives existing WEP constraints and whether the anisotropic channel is non-redundant with the standard anisotropic stress piₘuₙu. This draft remains suitable for specialist feedback, not arXiv submission.
H. J. Kang (Mon,) studied this question.