The reduction in the spacecraft length from the observers framework at velocities approaching the speed of light is an entirely different concept to perspective distance. Gordon-Smith used a cavity resonator to calculate the speed of light by measuring its wavelength and frequency. Wavelength l is the distance between two waves of energy traveling from one point to another point.
If you set the iterations on the animation to a low number eg.
Just select the layout enter the rooms dimensions and hit calculate. The result of this should be the total energy contained in the mass. Gordon-Smith used a cavity resonator to calculate the speed of light by measuring its wavelength and frequency. The results may contain very small precision errors but these wont usually overly affect the results see below for an explanation.