The game manual says the defenses are each 4ft 2in. The field drawings say they are 48 inches (4ft). Which measurement are we going off of for the defenses?
Field Drawings have more authority over the Game Manual iirc.
If you want to be doubly sure, the Q&A is always a good place to ask
Which field drawings? The Team Drawings sometimes have dimensions slightly different than the field (for example, 50"->48") in order to ease construction (in this case it lets you use the 4’ dimension of a 4’x8’ sheet of plywood.) Drawing GE-16010 in the official field drawing package shows the 50" dimension of the defense platform base (“Defense Carrier”) and GE-16016 shows the 50" dimension of the baseplate for each defense.
I don’t know what “field drawing” you’re talking about, but the Defense Base (Drawing GE-16016) clearly shows that it’s 50 inches (4 ft. 2 in.) wide. That means the defenses are 4 ft. 2 in. (50 inches) wide.