I've used SymPy in a very similar way, in my case it was some nasty derivatives that were needed for some orbital mechanics calculations.

First write down the equations, then let SymPy do the laborious math part and turn the output into C code.

I'm guessing this is why you don't see a lot of SymPy projects in the wild. It was used for some intermediate calculations, and the results were turned into the product's code and the symbolic code is thrown away.