If you haven't, open a ticket. I have had a few issues and both have been resolved in less than a few days because I opened a ticket for the issue. There is nothing they can do for you if you don't open one.
Even at 4 players it can get bad, but up to 5 or 6 and it gets near unplayable at times. Anyone else having this issue? I have a 16 slot server, so this shouldn't be an issue theoretically? I understand it could just be the server's aren't optimized well from the devs etc, but an acknowledgement from survivalservers.com or other people with this issue would be great!