That is how I do it. I aim for:
DL/DC
DR/DC
MR/DMR
ML/DML
AMR/AMC
AML/AMC
DMC/DC or DMC/DML or DMC/DMR
after a few seasons, those seem to be the best combinations for covering injuries. If you go with AMR/MR or AML/ML you will be short AMC and if your AMR/MR gets injured, you will probably have to use red packs for heal him (depending on the formation you use, but your formations are more midfield based, so it may not be a problem for you).