"willing"? Not exactly. But if you computed the steel plate deflection from a formula in Machinery's Handbook, you already know how. (I got the same result.) Your mission, if you agree to accept it, is to establish the Modulus of Elasticity (E) for plexiglas. As a rule of thumb, for equivalent deflections, aluminum should be about 1.5 times the steel thickness, and wood should be about 3 times.