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Is there a way of setting it up so that only 1 log per day is created instead of 2? I believe that this is preventing clicktracks from seeing the referring URLs for completed transactions.
Plesk has a way to override virtual host settings by creating your own vhost.conf and vhost_ssl.conf files in the "conf" directory for that particular site configuration. In those files you could set up your new Apache error log handling mechanisms to point to the same logfile using the same format.