Basically drop tanks were not flown with unless they were needed for the most part. These are short tactical missions here. I know its a Melee Arena tactic (that I use) to take say DTs and 75 fuel...or perhaps DTs and 100 fuel and attack at T+60 in the hopes that the defending fighters will have no gas left. That is a game tactic not a WW2 tactic. So they are left out of this particular setup. So no DTs for the P-39s and no DTs for the 109s.