I've perhaps found out one of the major contributors to the high amount of lag.
While a weekly reboot may seem like enough, a semi-weekly server reboot will help keep the lag as minimal as possible. Of course, that would mean designating the reboot days, but that shouldn't be an issue.
I'd suggest Monday and either Thursday or Friday, since that allows players to play during the weekend with less lag and people can play during the week days with less lag.
Now by "reboot", I don't mean "close the server for like a day", I mean simply shutting off the server and turning it back on, maybe even restarting the host computer in the process.
While that may mean a minor loss of time where players can play, it would greatly reduce the amount of lag, allowing players to better enjoy their time online. This would be extremely great for players playing Co-Op and maps like Lizard Crisis.
