The B-21 program learned a lot from the B-2 both involving both positive and negative aspects. The B-2 was proving out and developing the new technologies, hardware/software and manufacturing techniques in order to build and produce a large LO flying wing bomber aircraft. CATIA, Solidworks, etc did not exist, Northrop had to develop it's 3D design database. I was on the B-2 from 1986 to 1996 and we did a lot exhaustive modeling, simulations, including ground and in-flight hardware in the loop testing, we had some very exceptional lab facilities and capabilities within Northrop, lots of company investment. The B-21 can and it seems has capitalized on these experiences.