NFS - linux server, mac client

I have a directory on my linux box I'd like to share with a mac laptop. I got it working with NFS, but I had to open up the permissions on the directory to everyone. I'd like to have a little more security. I created a group on the Mac and linux with the same GID. Set the group for the file and directory, and rw permissions for group. Now, when I access it from the mac, I'm getting a permissions error.
My /etc/exports looks like this:
Code:/export 192.168.1.0/20(insecure,rw,sync,no_subtree_check,crossmnt,fsid=0)
/export/Gnucash 192.168.1.2(insecure,rw,sync,no_subtree_check)[192.168.1.2 is the mac laptop]
Suggestions?