[CentOS] NFS4 idmap question

HTTPD on some of my CentOS5 systems is configured to run as user "nobody".
Also, it needs access to some exported file systems. CentOS5 uses NFS3 so I
changed the ownership of the files on the storage server to "nobody" to
give httpd full permissions.

Now I want to rebuild these systems with CentOS6 and httpd running as user
"apache". The problem is how to give access to the NFS exports to these new
servers while the old ones are still using the same exports.

CentOS6 uses NFS4 so I was thinking to use idmap and statically map user
"nobody" to local user "apache" but I can't seem to get it working.

I wonder is it even possible considering that user "nobody" is a system
type user?

Any better ideas what I can do to give user nobody on CentOS5 and user
apache on CentOS6 full access to the same NFS exported directories locally
owned by user nobody?

Thank you,

-- Peter