I was shooting offline, as you do with a broken hat-switch, and I noticed the B-24 seems to have a top fuel tank, right in the centre of the wings. I quickly looked online and it isn't clear. Mostly I see life dinghies housed there.
Also the B-29 seems to have fuel tanks in the nacelles of №1 & 4, but they're harder to ignite Similarly the B-17 seems much harder in general than the B-24 to set ablaze. Better protected tanks? Rubberised? Inert gas-filling?