[CentOS] How does /etc/sysconfig/networking/profiles/ work?

I have two routers for different subnets and I'd like to set up
different eth0 configurations depending on which one I have the
network plugged into.  However, it seems that every time I let
system-config-network do its thing it forces all the eth0
configurations to be the same  (hard-links them all to the one in the
"default" profile).

I'd also like to have virtual interfaces configured differently in
different profiles -- as in, not configured at all in some profies --
so I tried creating e.g. ifcfg-eth0:1 in one of the profiles/
subdirectories, but not only is it ignored when using the network
control tool to switch profiles, it also gets *deleted* from the
profile if I run system-config-network.

There's nothing about profiles in
/usr/share/doc/initscripts-7.93.20.EL/sysconfig.txt and no
documentation included with the system-config-* RPMs.  Does this
simply not support having different devices in different profiles? 
This (particularly the deleting of files I hand-edited) is the sort of
thing that used to make me rip linuxconf out of the older RedHat
distributions.

On a similar note, my ISP has four nameservers, plus I want to include
my local LAN nameserver and the nameserver from my work network -- but
system-config-network insists on deleting all but the first three
nameservers from my resolv.conf.  Yeah, I know, upstream issue, but as
long as I'm venting ...