rex and sfsagent forwarding

Reading the rex whitepaper, it says that "when a user logs into a remote
machine, he should see the same file systems as on the local machine".
I take this to mean that when I mount an sfs filesystem such as 
/sfs/@sfs.fs.net,uzwadtctbjb3dg596waiyru8cx5kb4an, then rex to another
machine, I should be able to see that filesystem in /sfs on the remote
machine, provided I've previously started sfsagent on my original 
machine and that sfscd is running on the remote one. 

However, I'm not finding this to be the case - when I rex to the remote
machine, I get a message about the agent getting forwarded, but the /sfs 
directory on the remote machine remains empty. Any suggestions?

Thanks,
David