Chad,
You may want to reassess my grade Sometimes your sources should be questioned. According to my sources, the B doors were changed because the area at the leading edge of the inner doors had to be deepened in order to properly meet the deeper sheet metal of the Merlin engine's installation. (That's also the reason the LEX were changed.) Notice on the attached photos where the leading edge intersects the fuse. on the XP-51...also notice where the leading edge appears to "break" downward, relative to the gear leg. The "B" wing breaks immediately inboard of the main strut and angles more downward. Now look at the depth difference of the fuselages where the leading edges intersect the fuselages. (A Picture's worth a 1,000 words.)

Learning's a wonderful experience, isn' it?