As Floppy Link says, its the angle.
When the TFC fuel tanks were removed and replaced by the metal tanks with hydrant piping it was all fitted along the back edge behind XR529's tail, with a line of Armco to prevent squaddies jumping out at night from falling down the (fairly substantial) slope, and there was still plenty of space.
Dungannon later became one of the least popular dets for TSW as, because of the catholic school right next door, restrictions on a/c movements were tightened up and thus it became a very slow, visitor free site.