I'll post some screenshots when i've the time tonight because i'm busy outside right now. But i just had to praise and praise and praise this amazing 4231 tactic! Like what ChristianEriksen said in the OP, it's very IMPORTANT that you give this tactic sometimes. I arranged 8 friendlies ( 4 wins, 4 draws) and as you can see, it's not really good given that i'm Man United but during this 8 friendlies it's all about understanding tactics and squad harmony. After this 8 friendlies, i'm 12 games into my season so far with a 9-2-1 record. The loss was away to arsenal 2-1 but i dominated the match and the 2 draws (sometimes you just don't know what happened). I also realised that that IF is very important in this tactic. I signed Eugene Konoplyanka for 7M for Dnipro and 12 games into the season, he had returned my with 8 goals and 8 assists. What a steal signing this must have been.
Another thing i realised is that team-talk is very important !!! I'll briefly explain what to do on different situation.
Before match : Ask the team to continue where they left off (calmly), but this only applies if your teams is on a good run
else, tell the team you expect to win the match (calmly)
Half-time : if win by a goal or 2, Don't get complacent (calmly) and tell your Defenders, Midfielder and Strikers that (There's more to come and i believe you got what it takes - something liddat)
if draw or lose: Show me somethings else or I'm not happy with your performance (aggressively) and tell your Defenders, Midfielder and Strikers that (There's more to come and i believe you got what it takes)
Full-Time : If win (I'm very happy with your performance (calmly) and tell your Defenders, Midfielders and Strikers that you're impressed with their performance)
If draw or lose There's not much other than winning this match is unacceptable - something liddat as well (aggressively) but an important things to take note is that you must analyse the game on the draw/lose and tell the team that they're unlucky on occasion.
During the match, I keep telling my player to concentrate whenever I've just score so that they keep the level of performane up. Usually i do this every 15-20 mins in the game. But if you concede a goal, encourage the team. If still draw or losing at 70mins mark, ask your team to push forward or demand more. If you're dominating the game but not scoring, ask your team to get creative. If drawing at half-time, ask your team to work harder(Demand More)!
Hope here are some tips and helps to guide you through a successful season and lastly, have fun with this tactics