[Seaside] Not enough space / semaphore error

[Phil (list)]

I was doing some basic stress testing to see what would break first
under load and got an error: 'Not enough space for external objects, set
a larger size at startup' in VirtualMachine #maxExternalSemaphores:.  I
could probably increase the limit (it appears to be 256 or so by
default), but the simulated load was far above what I'd ever reasonably
expect to see unless being (D)DOS'd so what I'd like to do instead is
limit the max number of sessions and/or requests that Seaside will
attempt to handle and ideally have any requests above the limit receive
a 5XX response... is this doable?

Thanks,
Phil