I was running an 8MB system until 6 months ago.  However, it
would go into swap hell if I tried to make kernels
locally.  It was only usable because I did most things were
done on a cpu server.

With 16mb, you can still run bigger screens than 640x480x8.
at 16MB on a terminal the kernel gives 60% of the memory to
the kernel.  You can make it more still if you want by
including in plan9.ini

	*kernelpercent=90

for example, to get 90%.  Of course, that leaves precious little
for processes.