recently, i was chatting with the admins for a private server and we wandered into discussing foundation blocks and their impact on lag.
as i understand it, foundation blocks seem to cause a lot of lag for players as they come into an area. it also impacts loading in as the same effect occurs for the base owner.
As the lag only seems to come from foundation blocks, this got me thinking it may have to do with under-mesh checking.
if this is the case, i would request the ability for PVE servers to toggle this feature off. This should radically improve performance as all those checks are no longer required.