I love the writeup, cant wait to go home and try the program. Because I cant wait, I gotta know a few things...
What kind of integrator is used, as in 1st order Euler, Runge Kutta, symplectic, or so on...?
Does the sun have finite mass? i.e. If we make Jupiter just as heavy, do we get to see the solar system as binary?
And finally, now that you are this far, I am interested in wiring in weak field general relativity to see precession of Mercury. Sounds like you used realistic physics constants, right?