I have disabled ipv6 permanently since F14, and no problem. Just add
"install ipv6 /bin/true to /etc/modprobe.d/dist.conf"(old variant) or
"blacklist ipv6" to /etc/modprobe.d/blacklist.conf and
"net.ipv6.conf.all.disable_ipv6 = 1" to /etc/sysctl.conf. There is
nothing you cant control in your Fedora setup.