It depends on difference between quality of your players and quality of opponent's team. Assymetry is good in exploring your advantage in such a sector of field (for example your AML>opponent's DR), but it also leaves a gap in other sector. If your opponent has good player in this gap, there is a risk of lose...

Assymetric formation are also harder to counter than standard ones. In the past, sometimes I used weird 4-5-1 like:
DL,2xDC,DR,DMC,MC,MR,AML,AMC,ST or ending like:...MC,MC,MR,AML,ST. Effects were always "strong": high victories or high defeats, depends on opponnent's reaction. If you want, you can also experiment with trick - attacking "weaker" flank (if your formation looks like you attack left flank, set passes on right flank, if it looks like you will attack flanks, set passing to center, etc.).