Northrop XST, the plane concept that lost out to what ultimately became the F-117. Also the great grand daddy of the B2 and the YF-23.
Depending on the 3D printer adjustment ratio, Stl files do not need to be processed, just slice them directly. I made the mold parting for a PLA printer(FDM)(render in blue). A resin-printed version is also available(render in yellow).