Sorry for the delay, I was travelling internationally, but am back home now.
I've just spun up RHEL 5.x in a VM locally to see where things are installed.
It looks like Infiniband support on RHEL 5.x stores everything in files under /etc/ofed/, unlike RHEL 6.x.
There is an /etc/ofed/openib.conf file in there. Have you tried changing the setting in there yet?