First of all, I'd like to not recommend you to do this because it will bring a lot of trouble for you (File Permission, R/A/W Speed per File Size/Total File Qty, etc).
BTW, the SFU's performance and security is not same as a Unix NFS Sharing. In fact, its poor. I do not suggest u to use this for large data access and high security requirement environment.
From your Error Message it seems that you do not have setup the Folder Owner.Pls. try to key-in the UID in the Anonymous UID and GID in the Anonymous GID in the "NFS Sharing" Tab. Do not...