In make.conf, EMERGE_LOG_DIR can be defined so as to specify "the location of emerge.log and emerge-fetch.log". It would be nice if qlop were to look for $EMERGE_LOG_DIR/emerge.log in the absence of the -f parameter, rather than /var/log/emerge.log.
fixed in git now: http://gitweb.gentoo.org/proj/portage-utils.git/commit/?id=eeb816f6dcf9a634303e3f1bd1e43d472a3fcff6