For the record, Saxton Hale and ZPS lag like shit when other servers are full also. ZPS has had a really bad lag problem recently, and really it's kind of always been there since it was on the box. Anytime any of the other servers filled up when ZPS was pushing 20 people, everyone's ping would shoot up and I look at our other servers and their lagging too. ZPS isn't a game that works well with lag, because then zombies start teleporting and attacking you from far away, which is VERY fucking irritating.
Doubt it's related but I'm really close to posting a really angry thread about finally upgrading the Serverbox RAM, which was suggested months ago. I'm sick of people asking me why the server sucks so bad, then I have to explain why, or they just ragequit after saying fuck this server I'm going to play where it isn't laggy. etc.