C3 venom 36/ IS 101/ 7.0 - Very good combo. Can not even compare to the stock fin. Not advicable to use the stock fin. Its a waste of time trying to tune w/ it. You will never see the potential of the IS 101 w/ the stock fin.
At the optimum tuning settings (ie, mast track pos., foot straps, boom height etc. ) the stock fin will spin out.
Its like putting bicycle tires in a ferrari