Well, if the custom slots on offense are any indication, the DC is filled out in order because to run wildcat you have to put the QB in a TE custom since the TE slot is filled before the QB slot. I'd assume the same thing happens on D, but what that exact filling order is I have no idea. Could be LDE/NT/DT/RDE/ROLB/MLB/LOLB/CB1/CB2/SS/FS or could the the reverse or even the D backfield first etc... guess you just have to test it in a game and see which slot he get's placed into on the first play. Might give some sort of clue.
Or maybe I'm just way off on how DCs get filled.