Finally, SWSoft has come to the party and added piped logging into the Plesk configuration. This is simply fantastic since it has enabled me to run many more websites on a shared hosting server. Yay!!
To enable piped Apache logs, do the following:
# mysql -uadmin -p`cat /etc/psa/.psa.shadow` psa -e "replace into misc (param,val) values ('apache_pipelog', 'true');"
# /usr/local/psa/admin/sbin/websrvmng -v -a