I agree with the 100%/0% guys and I have since the days of GD 1.0 (back then it was Always Run or Always Pass, but same outcome). I want to leave as little as possible to the Sim engine to decide.
So if you want anything not 100% or 0%, you're just going to have to accept the fact that you're not likely to get your desired percentages. I disagree with Support that "over the course of a game, you should see something near your percentages." Maybe in some games. That may be true over the course of a full season of games, but from game-to-game, I believe the sample size is too small to *always* converge close to your settings.