4-5-1 V-style is one of the most versatile formations. It can easily become defensive or offensive with the change of a few arrows. A great jack of all trades, but it's lack of defensive wingers can be exploited.
When playing against 4-5-1 V, you need to protect your flanks and attack the opponent's. Forget about attacking the middle, it's that simple. Keep in mind that 4-5-1 V-style is most often played with counter-attacking orders, so you don't want to overdo your attacks. Use normal or defensive mentality and press your own half.
As always, when playing against a midfield formation, you need to have at least as many midfielders as the opponent.
4-3-2-1
This is 4-5-1 V-style's brother. It takes advantage of not using a DMC who won't be blocking an nonexistent AMC and vice verse. This translates into a more powerful midfield to feed passes to the forward players.
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AML-------------------AMR
------MC----MC----MC----
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DL(UP)--DC--DC---DR(UP)
Motivated 4-5-1 flat.
While an unmotivated 4-5-1 flat would probably succumb to a 4-5-1 V-style, you can take advantage of that and make the opponent underestimate you. He'll probably realize that his flanks are under constant attack after a few goals.
----------------ST------------------
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ML(UP)--MC--MC--MC--MR(UP)
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DL(UP)-----DC---DC-----DR(UP)