[CentOS] X defaults

I've been trying to move from Centos 7 to fedora. My monitor is 1440x900, but fedora only believes it's 640x480. Grrrr. xrandr has not helped. I've been trying to write X configuration files to tell fedora 1440x900, but no joy. Is there a way to get X to tell me its current beliefs, very preferably in configuration file format?

According to the log file on Centos, everything was defaulted or probed. It contains no numbers. My guess is that fedora has different defaults and they are wrong for me.

I've had problems like this before, so I'm unwilling to install until I know I can run a live version. That makes life clunky. I have to boot to non-graphics, do my editing and change the runlevel.