A direct test of the mass-dependence of the force on a charged capacitor plate: Two tabletop null experiments, with a parameter-free optical prediction

Pre-registered experimental proposal. Two complementary tabletop tests of the mass-independence of the electrostatic force on a capacitor plate: (I) differential weighing of a mass-asymmetric capacitor in vacuum, and (II) folded optical path across the charged gap. Predicted signals are stated in advance of execution.