75% and DT's? where were you flying to? 75% is more than enough in that bird...if fight is close to base then 50%. Anything more than 75% is to much...this is of course in regards to MA flying.
Sometimes one has to go along way... What happens if you take off on 50% fuel to defend field and field is taken??? (talking about normal planes, not exceptionally long range planes like P-51)
If I have 75% +DT(they cost nothing and can be dropped right on the runway) and meet enemy aircraft I just drop the tanks, and am with a reasonable weight to fight.
In other planes which have shorter ranges, I use 100% + DT's, using main tanks first, to reduce weiight in case I have to dogfight. Then, I use fuel in DT's, if enemy IB, release the tanks and am all set.

In Special Events, in a fuel crictical mission, I would take off with 100% + DT's and use DT's fuel first.
Once, in Battle of Britain Event, flying Bf109's, had a nice wingman and our squad leader started to give us order to fly constantly changing headings, we never met the enemy. we were only sightseeing over England...

Made some mental calculations and found out that fuel was insufficient. Called leader and told him we were RTB on low fuel.

We flew back to base, climbing as high as practical, shutting down engine, reducing prop pitch, and gliding as far as possible. Then turning engine on and repeating procedure. Climb, shutdown, red. pitch and gliding.
We returned to base although wingman's engine quit on final due to fuel starvation. (Had told him not use WEP, unless in EMERGENCY, but he used it...) We were the only 2 remaining after the mission...
Used to fly for an airline and we had a nice phrase for that: "Women, runway(length) and fuel, one does not despise ..."

Mutley