I have always Beat 4-5-1 Flat teams 4-0 home and 2-0 away with this formation:

Play defensive on the Counter..

Something like this:

-DR-DC-DC-DL
----DMC-DMC-
-------MC-
---AMR- -AML-
--------ST-

:Mentality -Defensive
Focus:Both flanks
Own Half
Mixed Passing
COUNTRER ATTACK-YES
Red Arrows on AMR and AML

Good Luck.
Post Result Please