Thank you!
No, my formation depends on my opponent. This is my "standard" formation:
-----------ST-----------
----------AMC----------
-------MC-MC--MC-------
DML----------------DMR
------DC--DC--DC-----
-----------GK----------
Now if my opponent plays with an AMC, i will use a DMC and only 2 MCs. If my opponent plays with an DMC, i will remove my AMC and play with 2 STs instead. Additionally, i can change my DML/DMRs to DL/DRs or remove an DC to add an extra ST (then i have DL DC DC DR).