@SGP posted:That seems a bit backwards. When you have a variety of alternative designs already fulfilling the role a 4-8-4 would service, I don't see what the need for a 4-8-4 would have been.
Maybe a "modern" Super Power 4-8-4 would have been better/cheaper than double heading K4s Pacifics all the way to Chicago and back in the late 1930s thru the late 1940s.