I am drawing a 3D surface with the following code:

S1 = 
  Plot3D[-69*(Cosh[(3*x)/299] - 1) + 200, {x, -200, 200}, {y, -1, 1}, 
    Mesh -> None, 
    BoxRatios -> {1, .1, 1}, 
    ColorFunction -> "Rainbow", 
    PlotPoints -> 40, 
    PlotStyle -> Thickness[10]];
Show[{S1}, Boxed -> False, Axes -> False]

As you can see, I am attempting to increase the thickness of the function with the following term:

PlotStyle -> Thickness[10]

Yet, this does nothing. It stays thin. I have also tried changing the constant from 10 to .01. But this does nothing too. I have browsed the Wolfram documentation page and this forum, but I cannot quite find a solution. I appreciate any help with this.