I don't think base stealing stats figure into success rates in taking extra bases in relation to the baserunning aggressiveness setting. And if you have a guy set to 0 on the individual base stealing, I don't think that stops him from trying to take an extra base if the team aggressiveness setting is 4 or 5. The speed rating will have the biggest impact on the success rate of safely taking the extra base. The setting itself will only determine how often guys go for the extra base.