spread deamon ip filtering?

We're using spread 4.0.0 on Linux.  We'd like to be able to do
IP-based filtering of clients.

>From the sample.spread.conf file included in the spread source:

#The current choices are:
#   NULL for default, allow anyone authentication
#   IP for IP based checks using the spread.access_ip file

#RequiredAuthMethods = "   "
#AllowedAuthMethods = "NULL"

So it looks like I would put the following in my actual spread config file:

RequiredAuthMethods = "IP"
AllowedAuthMethods = "IP"

But what about this "spread.access_ip" file---where does it live?  In
the same directory as the config file?  Or the spread runtime
directory?

Also, what is the format of the file.  Do I have to list individual
IPs, or can I specify subnets?  If can specify subnets, what is the
format (e.g., 192.168.1.0/24 vs 192.168.1.0/255.255.255.0)?

What if I have two spread daemons running on the same server, and both
need different IP whitelists?

Thanks!
Matt