Hi,
just FYI: I've added some info about the sizes of netinst/businesscard to
the web page <http://www.debian.org/CD/netinst/>. Having searched for a
while on the net, I chose 180 MB (netinst) and 40 MB (businesscard). The 40
MB are just a rough figure, business card CDs are available in a variety of
sizes.
Most arches don't exceed these limits, but some (most notably ia64) do.
However, ISTR someone saying here quite a while ago that the sizes are
really only checked for i386, so I guess this is OK.