[PureParadigm]

Thanks for the suggestion. I'll look into whether a VPS is viable, but we often have poor internet at our LAN parties and get the best experience when the server is local.

It's a vanilla server and I also get around 4 players. The real problem occurs when people are generating new terrain while flying on an elytra, sometimes causing the server to crash altogether. When not exploring, it will frequently report "Can't keep up!" messages even when hanging around spawn, which I think might be due to the truly insane amount of hoppers we have (although haven't seen this as much in the recent update).

If you're curious, the CPU is a i5-3570K @ 3.40GHz. The game is certainly playable, but it struggles under load like I described.