This is nearly impossible to have FULL droptank in the middle of dogfight, 'cause you must calculate fuel consumption and the fact, that every pilot uses droptanks first. And when droptank's fuel level is approaching 0, or, let's say, a half, then fumes might be enough to cause explosion, even with ordinary shell, or bullet. And don't forget about big hole, which is giving more and more oxygen to the burning fuel, so it's quite possible to blow a droptank, and is proven by some guncam vids of WWII period.
__________________
|