Why Eppley and Hannah's Experiment Isn't
  It is shown that Eppley and Hannah's thought experiment establishing that gravity must be quantized is fatally flawed. The device they propose, even if built, cannot establish their claims, nor is it plausible that it can be built with any materials compatible with the values of c, h, and G. Finally the device, and any reasonable modification of it, would be so massive as to be within its own Schwarzschild radius--a fatal flaw for any thought experiment. 
James Mattingly