I take 100%, no DT.
You guys have to be kidding

. I never carry 100%. With a lot of the planes 25% is all you need to fight around your own base- 50% to get you to another base and back.
I use drop tanks fairly often in the Nikki. I normally load 50% with the nikki due to its small tank (or high fuel burn...don't know which it is). If I'm heading to another field and there's been little to no resistance, I'll go 75% which seems to work fine if I don't get interrupted on the way to the enemy field.
I don't like getting jumped with 75% fuel, though. If there's cons intercepting me on the way to the base, I'll use a drop tank and carry 50% of fuel and dump the drop tank if I run into trouble on the way to the target.
At least you guys have answered one question for me: I've run into a number of opponents that seem to have an endless supply of fuel in their planes as they seem to hang over my field forever. I was wondering how they did that as I couldn't imagine anyone crazy enough to take 100% fuel with them. I guess there are some that crazy.