I know it was looked down upon to strategize between matches (IIRC darkness was upset) what is the time limit that we have in between matches to switch cards?
Keep it to the minimal.
Let your opponent know how long you will need so they are not waiting.
If there is an extensive delay that the opponent is not aware of, report it to a Warmaster or SG.
Deliberately stalling out an opponent or running out their time will not be looked upon favourably if the pairing is not completed.
Oh and the Upgraded cards must stay the same right?
You can only remove cards, not change their upgraded status or not.