MIX and NFS

Now that Mark sadly is no longer with us, maybe I can raise this without 
getting my head bitten off.

We are using UW imapd 2007 with MIX format mailboxes.
Our storage expert would really like to use an NFS-mounted volume on a
native ZFS appliance, saying it's much better for snapshots and 
block-oriented backups than iSCSI.

Given that we are only trying to support one flavour of Unix (Linux), and 
possibly using NFS4 on Centos6/Linux 2.6, is there still a problem with
NFS, if the only processes opening mailboxes are using c-client libraries 
(dmail, imapd, mailutin, alpine) ?

I have read some of the copious texts about Sys V and flock() and am not 
sure what applies to Linux.