NFS export question && diskless dirs

[mr. phreak]

hi. I have a question regarding NFS-exports.

/etc/exports
/diskless/ro    -ro -maproot=root leia
/diskless/kernels leia
/diskless/rw   leia
/usr    -ro -alldirs leia
/home   -alldirs leia
/etc    -ro -alldirs -maproot=root leia

but mountd only recognize /diskless/ro - /usr - /home/ and /etc 
(showmount -e). How can I export

/diskless/ro -ro && /diskless/kernels with rw && /diskless/rw with rw 
tothe same host???

Also, I have another question. Is it possible to run a diskless system 
with /var and /tmp mounted
on a NFS-mount instead of using memory-disks? If possible, I'd gladly 
appreciate some tips or
links.

Best regards,
J