Can flat five at the back be effective?

The question is if 5 flat at the back can be effective? I will be playing that this season. If I have bad results, I will change orders instead of formation. 5 flat at the back is DL-DC-DC-DC-DR.

For example 5-3-2 Memer style has had a lot of success in this game. That is an offensive minded 5 flat at the back. More defenders usually work better with defensive mentality though, at least from my experience, so I will go Hard defensive in the beginning. And no counter attack, counter attack did not give me more goals last season so I will not be using that. I play GK-DL-DC-DC-DC-DR-ML-MC-MC-AMR-ST no arrows.

The first leg of the Cup was encouraging. We had more possession, the opponent had slightly more shots and more shots on target as well. At halftime it was like 3-1 shots on target. 0-0. Last two seasons I would have changed a lot to get more shots on goal, but this time I am patient. I did not change orders, and it was the right move, won 3-0. Maybe the opponent players tired in the 2nd half?

What is your opinions, can it be effective? What is your own experience with 5 flat at the back?

A little update, most games worked well so far, but had to losses already when opposition (same quality, but several players out of position they had, should have been a victory!) play with a 5 flat midfield. 3-5-2 and 4-5-1 both flat. This is something I will watch carefully in games to come...

Nothing is effective vs. trolling formations...