Hi billit,
On my LS Pro Duo 1TB Time Machine is working fine. Not out of the box but with a minimum of manual work. I really hope that you can understand my English because I'm not good in English (I'm from Germany).
First of all you have to choose if you just want to fill up all your available space on the network share with the time machine-stuff, because there is no possibility of a quota on the networkshares. If you set up a time machine backup (I explain how to do this later on) just on the LS Pro it will fill up all your free space with the backup in the next couple of month and you are not able to reduce the file-size manually to make more free space for other things. If this is ok, simply enter the following line in a terminal windows of Max OS:
defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1
This command will allow you to configure Time Machine with every mapped network drive (possibly logout and login to take effect).
Using a network share as backup medium, TimeMachine will use a so called sparesbundle to store the data. The sparesbundle will automatically increase its filesize if needed. The trick is now to limit the filesize, that we have enough free space for other stuff.
This is a little bit tricky, as we have to build the sparesbundle by ourselves and not by timemachine.
The complete documentation including using the existing data of an old backup can be found in the following arcticle:
http://www.readynas.com/?p=253
This works fine for Buffalo's as well.
Hope this helps but you should know that timemachine is veeeeery slooooow by using network shares.
regards,
Peter