I faced this formation in associations today. Not sure if this is the best counter, but I won both with 4-5-1v. Changed to 3w-5-2v in 2nd half of 1st leg. Scores were 3-0 and 1-0 (I added a 2nd after he changed the tactic.

Attacking/flanks/short/off/low/normal/m2m/on.