Stretching WW2 Designs

Recall that the inline Allison-powered P-40, developed from a radial-powered
predecessor, benefitted from such an aft-fuselage stretch, improving its
fineness ratio, allowing for drag-reduction at the tailfin-rudder interface,
and even allowing for fitment of a low-pressure variant of the RR Merlin.
Had the stretched P-40 been given the Merlin 20 series engine, it could have
become a serious high-altitude competitor.

Ballasting was not usually a good solution. In the Spitfire, for example,
ballasting was not very efficient when used in conjunction with the wider
and heavier Griffons, rendering tricky handling and at least one
test-establishment evaluation calling for cessation of production of Griffon
variants for that reason.

"IBM" wrote in message
...
(JDupre5762) wrote in
:

I have been wondering why were so few WW2 aircraft designs "stretched"
in order to get more performance or payload?
SNIP