Could you tell me more about "you could replace the php compression with a perl module that compresses all pages, not just those cached."
This might be an alternative:
https://www.ubbdev.com/ubb/ultimatebb.php?ubb=get_topic&f=30&t=000049&p= It might be easier, though, to see if you can upgrade the server to PHP 4.05 or higher, so that PHP/zlib can be used.
