I have tried a full season removing the "Tackle Harder" player instructions and I finished 2nd with Blyth Spartans predicted 22nd.
The amount red yellow/red cards has drastically lowered. I prefer it this way since I don't like having unsportsmanlike players.
I'm playing with Blyth Spartans in the Vanarama North or South, can't remember right now. We were predicted to finish 22nd but we finished 5th using this tactic. I'm a total underdog. I won more than I lost using this tactic as an underdog team and that's a friggin' win in my book.