Stretching WW2 Designs

I have been wondering why were so few WW2 aircraft designs "stretched" in order
to get more performance or payload? I know of the FW 190D which was stretched
in the aft fuselage section in order to compensate for the installation of Jumo
V 12 engine. Could other designs have benefitted from the technique of
stretching in one way or another? Was it not done because the designs of the
era were not suited to it? In recent years even reworked C-47s have been
stretched. Was there simply no perceived need to stretch a design?

John Dupre'