Coincidentally, I came to the thread to mention this. I am still experimenting with how to increase fumbles and tried boosting the OxST to 255 for Humans and leaving it at 0 for the AI (with AI fumble on 199). (really, I am trying to find settings that produce NFL blitz type havoc in terms of fumbles, huge hits, etc.)
With this setting, I've noticed that my RTG avatar will simply pancake any player he touches when blocking--but, only if the other player is not running or, if he is running, then does not engage my avatar. That is, if the computer player engages my running avatar, there is still a realistic block interaction and not a pancake.