These options work for Kickstart to load the install tree from NFS: The Fedora Kickstart documentation states
nfs --server=nfsserver.example.com --dir=/tmp/install-tree --opts="username=u1,password=p1"
The RedHat6 documentation install guide does not mention the options flag but they are mentioned in the Fedora guide:
ks=nfs[:options]:<server>:<path>
How to add nfs options parameter to Anaconda in RHEL6.x?