Allow me to add my modest contribution with these two whiffs, which I think they are relevant to this topic:1°) The
Lockheed CL-1860 Bright Star was an original attempt from Lockheed to produce a naval observation type at a reduced cost using elements of the U-2 spy plane. Though the length of the airframe was unchanged, the fin, rudders and wings were shortened (the latter being hinged for carrier use). 45% of the aircraft were taken directly from the U-2 production lines, and another 25% were modified from U-2 elements, leaving only 30% new, basically the cockpit and dorsal intake. The Navy evaluated the sole prototype in 1973 but tests were not conclusive enough to justify procurement.

2°) The
Lockheed YU-12A Twin Star prototype was proposed by Lockheed to the US Air Force as a way to augment the range and autonomy of the original U-2 spyplane. Apparently this was not conclusive and the experiment was halted.
