Nice, this is do-able. i got 200k on my first gen, but i was aiming for 500k-1M without shanty towns. I assume that isn't currently possible, but i hope it will be at some point
I think that with shanty towns (which really should be renamed "sprawl" or something like that) 500k is achievable, but 1m is not. This is not what one would expect from a *medieval* city generator anyway :)