West Coast
Looking at the pic of the Lightning, what was the goal of the engineers loading the engines on top of one another?
They are not stacked vertically: the lower/forward one is below the wing, the aft/higher one behind the wing - this layout enabled the minimum possible frontal area, as the widest bits of each engine were staggered.
A contemporary of mine worked at Warton on the Lightning (and TSR2); on the former, access to most things was very difficult. A review by EE later suggested they could have made the fuselage 3 inches wider, with negligible performance loss and much better access. Hindsight is wonderful!